Phase tracking reference signal transmission

ABSTRACT

A system, method, and device for ensuring a number of Phase Tracking Reference Signal(s) (PT-RSs) are the same for multiple slots. A wireless transmit/receive unit (WTRU) may receive control information including a number of scheduled resource blocks (RBs) then determine a PT-RS density based on the number of scheduled RBs. The WTRU may determine a RB offset value for the WTRU based on a WTRU-ID modulo the maximum RB offset value, where the maximum value for the RB offset value may be based on at least one of the number of the scheduled RBs and the PT-RS density. The WTRU may then transmit or receive a signal with PT-RS based on the RB offset value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional U.S. Application No.62/586,642 filed on Nov. 15, 2017, and U.S. Application No. 62/720,614filed on Aug. 21, 2018, the contents of which is hereby incorporated byreference herein.

BACKGROUND

In advanced wireless systems there may be high data requirements forspectrum above 6 GHz frequency in order to leverage the large bandwidthavailable. One challenge of using these frequencies may be thesignificant propagation loss especially in an outdoor environment due tohigher free space path loss in higher frequencies. Systems, methods, anddevices may be used to address these issues.

SUMMARY

A system, method, and device for ensuring a number of Phase TrackingReference Signal(s) (PT-RSs) are the same for multiple slots. A wirelesstransmit/receive unit (WTRU) may receive control information including anumber of scheduled resource blocks (RBs) then determine a PT-RS densitybased on the number of scheduled RBs. The WTRU may determine a RB offsetvalue for the WTRU based on a WTRU-ID modulo the maximum RB offsetvalue, where the maximum value for the RB offset value may be based onat least one of the number of the scheduled RBs and the PT-RS density.The WTRU may then transmit or receive a signal with PT-RS based on theRB offset value.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings,wherein like reference numerals in the figures indicate like elements,and wherein:

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A according to an embodiment;

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an embodiment;

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A according to an embodiment;

FIG. 2 is an illustration of an example PT-RS time density;

FIG. 3 is a diagram of an example chunk-based pre-DFT PT-RS forDFT-s-OFDM with N chunks;

FIG. 4 is a diagram of an example normal cyclic prefix (CP);

FIG. 5 is a diagram of an example extended CP (Virtual CP);

FIG. 6 is a set of diagrams of an example plain UW and CP combination;

FIG. 7 is a diagram of an example perturbation approach;

FIG. 8 is a diagram of an example dynamic approach for DFT-s-OFDM;

FIG. 9 is a diagram of an example dynamic approach for DFT-s-OFDM;

FIG. 10 is a diagram of an example of PT-RS frequency density;

FIG. 11A is a diagram of an example of RB offset values;

FIG. 11B is a diagram of an example process for maintaining the samenumber of PT-RSs for a scheduled bandwidth.

FIG. 12 is a diagram of an example cyclic shift of RBs containing PT-RS;

FIG. 13 is a diagram of an example of PT-RS mapping for 7 RBs withdifferent RB offset values;

FIG. 14 is a diagram of an example PT-RS mapping for 7 RBs and 13 RBswide scheduling;

FIG. 15 is a diagram of an example PT-RS mapping for 7 RBs with dynamicRB offset values;

FIG. 16 is a diagram of an example of PT-RS mapping for 13 RBstransmission with dynamic RB offset values;

FIG. 17 is a diagram of an example PT-RS frequency location based onsymbol location;

FIG. 18 is a diagram of an example PT-RS frequency density based on RBG;

FIG. 19 is a diagram of an example PT-RS generation for pi/2 BPSK datamodulation;

FIG. 20 is a diagram of an example PT-RS generation for pi/2 BPSK datamodulation and OCC;

FIG. 21 is an illustration of example of cycling through OC does;

FIG. 22 is an example constellation of pi/2 BPSK and QPSK constellation;

FIG. 23 is a diagram of an example of common PT-RS design;

FIG. 24 is a diagram of an example OCC application;

FIG. 25 is a diagram of an example OCC application;

FIG. 26 is an example constellation of an alternative pi/2 BPSKconstellation;

FIG. 27 is a diagram of an example generating CP extending RSs based onpredetermined RSs with a CP extender block;

FIG. 28 is a diagram of an example signal structure to achieve virtualCP with the CP extender block;

FIG. 29 is a diagram of an example partitions of a waveform matrix toderive CP extender block;

FIG. 30 is a transmission diagram of an example NR numerology withvirtual CP;

FIG. 31 is a signal diagram of an example NR numerology with virtual CP;

FIG. 32 is a diagram of an example doubling CP extension withCP-extending RSs;

FIG. 33 is a diagram of an example CP extending PT-RS design;

FIG. 34 is a diagram of an example signal structure for virtual CP withCP extender block; and

FIG. 35 is a diagram of an example of the partitions of a waveformmatrix to derive CP extender block for complete PT-RS.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN104/113, a CN 106/115, a public switched telephone network (PSTN) 108,the Internet 110, and other networks 112, though it will be appreciatedthat the disclosed embodiments contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d may be any type of device configured to operateand/or communicate in a wireless environment. By way of example, theWTRUs 102 a, 102 b, 102 c, 102 d, any of which may be referred to as a“station” and/or a “STA”, may be configured to transmit and/or receivewireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106/115, the Internet110, and/or the other networks 112. By way of example, the base stations114 a, 114 b may be a base transceiver station (BTS), a Node-B, an eNodeB, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller,an access point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

As discussed herein, a wireless device may be any node on a networkcarrying out wireless communication, such as a WTRU or a based stationas described herein.

The base station 114 a may be part of the RAN 104/113, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals on one or morecarrier frequencies, which may be referred to as a cell (not shown).These frequencies may be in licensed spectrum, unlicensed spectrum, or acombination of licensed and unlicensed spectrum. A cell may providecoverage for a wireless service to a specific geographical area that maybe relatively fixed or that may change over time. The cell may furtherbe divided into cell sectors. For example, the cell associated with thebase station 114 a may be divided into three sectors. Thus, in oneembodiment, the base station 114 a may include three transceivers, i.e.,one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and mayutilize multiple transceivers for each sector of the cell. For example,beamforming may be used to transmit and/or receive signals in desiredspatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104/113 and the WTRUs 102 a,102 b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 115/116/117 using wideband CDMA (WCDMA).WCDMA may include communication protocols such as High-Speed PacketAccess (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-SpeedDownlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., a eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106/115.

The RAN 104/113 may be in communication with the CN 106/115, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. The data may have varying qualityof service (QoS) requirements, such as differing throughputrequirements, latency requirements, error tolerance requirements,reliability requirements, data throughput requirements, mobilityrequirements, and the like. The CN 106/115 may provide call control,billing services, mobile location-based services, pre-paid calling,Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication. Although notshown in FIG. 1A, it will be appreciated that the RAN 104/113 and/or theCN 106/115 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 104/113 or a different RAT. Forexample, in addition to being connected to the RAN 104/113, which may beutilizing a NR radio technology, the CN 106/115 may also be incommunication with another RAN (not shown) employing a GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106/115 may also serve as a gateway for the WTRUs 102 a, 102 b,102 c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104/113 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) anddownlink (e.g., for reception) may be concurrent and/or simultaneous.The full duplex radio may include an interference management unit 139 toreduce and or substantially eliminate self-interference via eitherhardware (e.g., a choke) or signal processing via a processor (e.g., aseparate processor (not shown) or via processor 118). In an embodiment,the WRTU 102 may include a half-duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for either the UL (e.g., for transmission) or thedownlink (e.g., for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (or PGW) 166. While each of the foregoing elements are depictedas part of the CN 106, it will be appreciated that any of these elementsmay be owned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In certain representative embodiments, the DLS may use an 802.11e DLS oran 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS)mode may not have an AP, and the STAs (e.g., all of the STAs) within orusing the IBSS may communicate directly with each other. The IBSS modeof communication may sometimes be referred to herein as an “ad-hoc” modeof communication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In certainrepresentative embodiments, Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA) may be implemented, for example in in 802.11systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed/detectedand/or determined to be busy by a particular STA, the particular STA mayback off. One STA (e.g., only one station) may transmit at any giventime in a given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications, such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 113 and the CN 115according to an embodiment. As noted above, the RAN 113 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 113 may also be in communication with theCN 115.

The RAN 113 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 113 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containingvarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, dual connectivity, interworkingbetween NR and E-UTRA, routing of user plane data towards User PlaneFunction (UPF) 184 a, 184 b, routing of control plane informationtowards Access and Mobility Management Function (AMF) 182 a, 182 b andthe like. As shown in FIG. 1D, the gNBs 180 a, 180 b, 180 c maycommunicate with one another over an Xn interface.

The CN 115 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whileeach of the foregoing elements are depicted as part of the CN 115, itwill be appreciated that any of these elements may be owned and/oroperated by an entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different PDU sessions with differentrequirements), selecting a particular SMF 183 a, 183 b, management ofthe registration area, termination of NAS signaling, mobilitymanagement, and the like. Network slicing may be used by the AMF 182 a,182 b in order to customize CN support for WTRUs 102 a, 102 b, 102 cbased on the types of services being utilized WTRUs 102 a, 102 b, 102 c.For example, different network slices may be established for differentuse cases such as services relying on ultra-reliable low latency (URLLC)access, services relying on enhanced massive mobile broadband (eMBB)access, services for machine type communication (MTC) access, and/or thelike. The AMF 162 may provide a control plane function for switchingbetween the RAN 113 and other RANs (not shown) that employ other radiotechnologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP accesstechnologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN115 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 115 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating WTRU IPaddress, managing PDU sessions, controlling policy enforcement and QoS,providing downlink data notifications, and the like. A PDU session typemay be IP-based, non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering downlink packets, providing mobility anchoring, and thelike.

The CN 115 may facilitate communications with other networks. Forexample, the CN 115 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 115 and the PSTN 108. In addition, the CN 115may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a localData Network (DN) 185 a, 185 b through the UPF 184 a, 184 b via the N3interface to the UPF 184 a, 184 b and an N6 interface between the UPF184 a, 184 b and the DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-ab, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

Generally, in LTE Orthogonal frequency-division multiplexing (OFDM) maybe used for the downlink (DL) transmission while a discrete Fouriertransformation (DFT)-s-OFDM may be used for uplink (UL) transmission. Inconventional Cyclic Prefix (CP) DFT-s-OFDM (sometimes referred to assingle carrier frequency-division multiple access (SC-FDMA) withmultiple accessing), the data symbols may be spread with a DFT block,and then mapped to the corresponding inputs of an IDFT block. The CP maybe prepended to the beginning of the symbol in order to avoidinter-symbol interference (ISI) and allow one-tap frequency domainequalization (FDE) at the receiver.

In the downlink transmission, reference symbols may be scattered overspecific subcarriers, (i.e., one OFDM symbol may have subcarriers loadedwith data and reference symbols). Common reference symbols may betransmitted on subcarriers distributed over the system bandwidth whileWTRU-specific reference signals may be distributed over the subband thatis allocated to a specific WTRU.

3GPP may address an advanced wireless communication system called NewRadio (NR). Applications of NR may be summarized under severalcategories: Enhanced mobile broadband (eMBB), Massive machine-typecommunications (mMTC), and Ultra-reliable-and-low-latency communications(URLLC). Under each category, there may be a wide set of applicationsthat are considered for various needs and deployment scenarios thatmandate specific performance requirements. For example, mMTC and URLLCapplications range from automotive to health, agriculture, utilities andlogistics industries.

To fulfill the high data rate requirements, spectrum above 6 GHzfrequency may be used to leverage the large bandwidth of that spectrum.One challenge of using these higher frequencies may be the significantpropagation loss especially in an outdoor environment due to higher freespace path loss in a higher frequency.

Beamforming (e.g., analog beam) may be a solution to address thesignificant path loss in a higher frequency since it can compensate pathloss without increasing transmission power. As beams are used tocompensate the path loss, all downlink and uplink channels may be basedon beams.

In one situation, Device to Device (D2D) and/or Vehicle to Everything(V2X) communication may employ LTE. One or more of the followingphysical channels may be used for sidelink transmission and/orreception: SPSS (sidelink primary sync signal) and/or SSSS (sidelinksecondary sync signal); PSBCH (physical sidelink broadcasting channel);PSCCH (physical sidelink control channel); PSSCH (physical sidelinkshared channel); and/or PSDCH (physical sidelink discovery channel).

A sidelink may support one or more modes (e.g., up to 4 Modes). A firstand/or second mode (e.g., Mode 1 and/or Mode 2) may be used for D2Dcommunication. D2D communication may require power efficient reliabletransmission. D2D communication may be delay tolerant and/or may be usedfor low mobility. Mode 1 may be based on or may use eNB scheduling forsidelink transmission, where a resource for a sidelink transmission maybe scheduled by the eNB via a DCI. Mode 2 may be based on or may useWTRU resource selection (e.g., autonomous resource selection) within aresource pool that may be configured. Mode 1 may be used when WTRUs forsidelink transmission are located under or within an eNB coverage sothat the WTRUs may be able to receive the control signal from the eNB.Mode 2 may be used when WTRUs for sidelink transmission are out of theeNB coverage and/or when they are within coverage.

A third and/or fourth mode (e.g., Mode 3 and/or Mode 4) may be used forV2X communication, for example to support high mobility and/or lowlatency. Mode 3 may use eNB scheduling for sidelink resourcedetermination. Mode 4 may use WTRU resource selection (e.g., autonomousresource selection).

For a mode using scheduling (e.g., Mode 1 and/or Mode 3), a sidelinkWTRU may receive a resource grant for sidelink transmission. The WTRUmay monitor (e.g., monitor for) the resource grant in a search spaceconfigured for a Uu interface.

In one or more embodiments, a phase tracking reference signal (PT-RS)may be used to measure, track, and/or estimate phase noise to compensatethe phase noise before the demodulation of a Physical Downlink SharedChannel (PDSCH) and/or a Physical Uplink Shared Channel (PUSCH). ThePT-RS may be interchangeably used with phase noise reference signal(PNRS), and reference signal (RS).

The PT-RS may be transmitted within a scheduled bandwidth for PDSCH orPUSCH. The transmission of PT-RS in the scheduled bandwidth for PDSCH orPUSCH may be turned on/off by a node, such as a gNB, via higher layersignaling. If the transmission of a PT-RS in the scheduled bandwidth isturned on, the presence of the PT-RS and/or density of the PT-RS (e.g.,time and/or frequency) in a scheduled bandwidth for PDSCH or PUSCH maybe determined based on one or more of the following: scheduled number ofresource blocks (RBs) (e.g., a.k.a. scheduled bandwidth and/or physicalresource blocks (PRBs)); modulation coding scheme (MCS) level indicatedfor the scheduled PDSCH and/or PUSCH; numerology (e.g., subcarrierspacing, slot length, etc.); WTRU capability (e.g., support PT-RS ornot); demodulation reference signal (DM-RS) density which may be usedfor demodulation; number of layers scheduled (e.g., transmission rank ofPDSCH or PUSCH); and/or presence of UCI in the PUSCH and its associatedUCI type (e.g., HARQ-ACK or CSI).

When PT-RS is present in a scheduled bandwidth for PDSCH or PUSCH, asubset of scheduled RBs may include, contain, or transmit the PT-RS. Thesubset of PT-RS RBs may be determined based on one or more of the RBoffset or scheduled bandwidth.

For RB offset, the subset of RBs that have PT-RSs may be located everyK-th RB within the scheduled bandwidth, where the RB is indexed from thelowest RB index within the scheduled RBs to a RB with a higher indexregardless of whether the scheduled RBs contiguous or distributed. TheRB offset may be the starting RB index to include PT-RS. As discussedherein RB offset, PRB offset, starting RB offset, and starting RB indexmay be interchangeably used.

For scheduled bandwidth, the number of RBs that may include, contain, ortransmit PT-RS may be determined based on the scheduled bandwidth. Afirst number of RBs may include PT-RS if the scheduled bandwidth issmaller than a first threshold and a second number of RBs may includePT-RS if the scheduled bandwidth is equal to or greater than the firstthreshold and smaller than a second threshold, and so forth. The subsetmay include the situation where all scheduled RBs (or RBs) may contain,include, or transmit PT-RS.

When PT-RS is present in a scheduled bandwidth for PDSCH or PUSCH, asubset of symbols (e.g., CP-OFDM symbols or DFT-s-OFDM symbols) mayinclude PT-RS. The presence of PT-RS in a symbol may be determined basedon one or more of the following: the MCS level (or modulation order) ofthe scheduled PDSCH or PUSCH; presence of DM-RS in the symbol (e.g., ifa symbol includes DM-RS, PT-RS may not be transmitted in the symbol);and/or PT-RS density determined based on one or more schedulingparameters. The PT-RS density, time/frequency location, and/or use ofDFT precoding or not may be dependent on the waveform used.

In one scenario, PT-RS may be used for PDSCH or PUSCH transmission whena CP-OFDM waveform is used. One or more subcarriers in a RB may be usedfor a PT-RS transmission; the same subcarrier location over consecutiveOFDM symbols, which may be determined for PT-RS transmission, may alsobe used.

FIG. 2 illustrates several examples of PT-RS time density. There arethree example grids 202, 204, and 206 where the horizontal axis 201 foreach grid may be OFDM symbols and the vertical axis 203 is subcarriers.For each example there is a grid of Resource Elements (REs) where shadedblocks may represent REs containing PT-RS. Looking from left to right,in example 202 there may be a PT-RS located in every symbol (e.g., OFDMsymbol), in example 204 there may be a PT-RS every 2^(nd) symbol, and/orin example 206 there may be a PT-RS every 4^(th) symbol. PT-RS timedensity may be determined based on MCS threshold, for example as shownin Table 1 below. I_(MCS) may be a MCS level used, determined, orindicated for PUSCH or PDSCH in an associated DCI. PT-RSthMCS1,PT-RSthMCS2, PT-RSthMCS3, and PT-RSthMCS4 may be configured via higherlayer signaling or a DCI and referred to as thresholds to determine thetime density of PT-RS. A default configuration may be used (e.g., everysymbol) if there is no configuration or indication

TABLE 1 Example time density of PT-RS as a function of scheduled MCSScheduled MCS Time density(l_(PTRS) ^(step)) I_(MCS) < PT-RSthMCS₁ PT-RSis not present PT-RSthMCS1 <= I_(MCS) < PT- present on every 4^(th)symbol RSthMCS2 PT-RSthMCS2 <= I_(MCS) < PT- present on every 2^(nd)symbol RSthMCS3 PT-RSthMCS3 <= I_(MCS) present on every symbol

For CP-OFDM and DFT-s-OFDM, when PT-RS is present, the PT-RS mappingpattern may start at the first symbol containing PDSCH/PUSCH in the slotand may then map to every L_{PT-RS} symbol. A PT-RS mapping pattern maybe restarted at each symbol containing a DMRS and then mapped to everyL_{PT-RS} symbol relative to the symbol containing PT-RS. In the case oftwo adjacent DMRS symbols, the PT-RS pattern may be restarted using thesecond of the two DMRS symbols as a reference. When PT-RS time densityis lower than 1, the symbol right after front-loaded DMRS and the symbolright after additional DMRS, if it exists, may not contain PT-RS. ThePT-RS according to the mapping pattern may not be transmitted in OFDMsymbols that contain PDSCH/PUSCH DMRS. The PT-RS according to themapping pattern may not be transmitted in a Resource Element (RE) thatoverlaps with a configured control channel resource sets (CORESETs).

PT-RS frequency density may be determined based on the number of RBsscheduled as shown in Table 2 below. N_(RB) may be the number of RBscheduled. PT-RSthRB0, PT-RSthRB1, PT-RSthRB2, PT-RSthRB3, andPT-RSthRB4 may be the thresholds to determine frequency density of PT-RSand it may be configured via RRC signaling or indicated in an associatedDCI. A default configuration may be used (e.g., 2nd RB) if there is noconfiguration or indication.

TABLE 2 Frequency density of PT-RS as a function of scheduled bandwidthScheduled bandwidth Frequency density (every K^(th) RB) N_(RB) <PT-RSthRB0 PT-RS is not present PT-RSthRB0 <= N_(RB) < PT- present onevery RB RSthRB1 PT-RSthRB1 <= N_(RB) < PT- present on every 2^(nd) RBRSthRB2 PT-RSthRB2 <= N_(RB) < PT- present on every 4^(th) RB RSthRB3PT-RSthRB3 <= N_(RB) < PT- present on every 8^(th) RB RSthRB4

FIG. 3 illustrates an example process where a chunk-based pre-DFT PT-RSinsertion may be used for generating a DFT-s-OFDM waveform. PT-RSinput/output 322 is shown with arrows and grey shading, and datainput/output 321 is shown with black arrows. Generally in LTE, theprocess of forming a waveform may involve the data symbols 302 initiallyspread with a DFT block 304, and then mapped to the corresponding inputsof an IDFT block 306. The CP 308 may be prepended to the beginning ofthe symbol in order to avoid inter-symbol interference (ISI) and allowone-tap frequency domain equalization (FDE) at the receiver.

A PT-RS pattern (e.g., chunk-based pre-DFT PT-RS pattern) may bedetermined based on a number of chunks (X) 310, chunk size (V) 312, andthe location of chunks. The X PT-RS chunks 310, such as PT-RS chunk #1311 may be inserted prior to the DFT block 304. The PT-RS chunks anddata would proceed along the same process as described above for forminga waveform. A chunk is comprised of tones, and for each chunk, and itssize may be V PT-RS tones. For each chunk, there may be V PT-RS tonesbefore the DFT input; in the example of FIG. 3 the chunk size may be V=3as shown with three long dotted arrows for each PT-RS chunk; this isalso shown in the resulting waveform in a DFT-S-OFDM symbol 313 wherethe PT-RS chunk #1 311 is in the first three shaded blocks and PT-RSchunk #X is at the end.

The location of the chunks of a DFT input may be determined based on thescheduled RB, chunk size (V) 312, and/or the number of chunks (X) 310.For example, two values of V, V₁ and V₂, may be used and the location ofthe chunks may be determined based on the V value as follows: when V=V₁,the samples in DFT domain may be divided in X intervals, and the chunksmay be located in the Head (first V samples), Middle (middle V samples),or Tail (last V samples) in each interval; and when V=V₂, the samples inDFT domain are divided in X intervals, where in the first interval thechunk is placed in the Head (first V samples), in the last interval thechunk is placed in the Tail (last V samples), and in the rest ofintervals the chunk is placed in the middle of each of the twointervals.

A PT-RS pattern may be determined based on scheduled bandwidth (BW) witha set of thresholds N_(RBn), n=0, 1, 2, 3, 4, per BWP that indicates thevalues of X and V that the WTRU should use depending on the scheduled BWaccording to the Table 3 below. Y represents any value. In one example,the value of Y may be 8.

TABLE 3 pre-DFT PT-RS pattern (X, V) based on scheduled BW Scheduled BWX × V N_(RB0) < N_(RB) ≤ N_(RB1) 2 × 2 N_(RB1) < N_(RB) ≤ N_(RB2) 2 × 4N_(RB2) < N_(RB) ≤ N_(RB3) 4 × 2 N_(RB3) < N_(RB) ≤ N_(RB4) 4 × 4N_(RB) > N_(RB4) Y × 4

FIG. 4 illustrates a diagram of a signal with a normal Cyclic Prefix(CP). Time 401 is shown on the horizontal axis. For any of the figuresdiscussed herein, each portion of any given symbol shown in a timedomain signal diagram may be shaded with a pattern to indicatesimilarity. As shown there are two symbols of a signal (i.e.,DFT-s-OFDM, OFDM), symbol 402 and symbol 403 with a CP 406 and CP 407respectively. In normal CP operation the size of each CP may be G andthe Inverse Discrete Fourier Transformation (IDFT) output may beextended by prepending a replica of the last part of IDFT output: CP 406and CP 407 may replicate the end and follow N-IDFT Output 404 and N-IDFTOutput 405 respectively, where the last part portion is 413 and 415respectively and indicated by arrows 410 and 411 respectively. At thereceiver side, the location of the DFT window may be on the first symboland may not capture a sample from the subsequent symbol: each N-IDFTOutput 404, 405 may be within a receiver (RX) DFT window 408, 409respectively. However, if the CP size G is not less than the number oftaps for the multipath channel, the receiver may suffer from ISI. Insome cases, the normal CP size may not be sufficient. For example, ifthe communication environment is outdoors or the link is established onnon-line-of-sight (LOS) paths, the maximum excess delay of the multipathchannel may increase substantially. In these cases, the duration of theCP may not be large enough to handle the delay spread of the channel andthis insufficient CP size may lead to inter-symbol-interference (ISI).

FIG. 5 illustrates a diagram of a signal with an extended CP (e.g.,virtual CP). Time 501 is shown on the horizontal axis. As shown there isa symbol 502 of a signal with a CP 506 that may be extended to length523. Note that a second symbol 503 with N-IDFT Output 505 and CP 507 isshown to provide context for where the extension comes from with respectto the entire signal. CP Extension (a.k.a., virtual CP) may be used toaddress when the CP size is not long enough. The goal of a virtual CPmay be to increase the effective CP length of the block-based symbols(e.g., DFT-s-OFDM, OFDM) to increase their robustness against multipathchannel. In the example shown in FIG. 5 the CP 506 of length G may beextended by H samples to a total extended CP length 523. The N-IDFTOutput 504 of the IDFT may be extended by prepending a replica 522 ofthe last part of the N-IDFT Output 504, similar to the example shown inFIG. 4, however, the extended CP regions may be forced to be identicaldue to the special structure of IDFT-output. Also note that the RXDFT-Window 508 may be shifted by H samples.

Since this approach may not change the basic receiver operations, it mayalso be beneficial to maintain the hardware-complexity at the receiverside. Another benefit of virtual CP may be the reduced out-of-bandemission (OOBE) due to the fact that two subsequent symbols are forcedto be continuous as the samples in the RX DFT window should becontinuous to decode the symbols without interference.

FIG. 6 illustrates an example of plain unique word (UW) and cyclicprefix (CP) combination. In one approach, UW and CP may be combined asillustrated. Looking at the Transmission (TX) Block Diagram 601, PT-RS602 a and 602 b may be mapped to both ends of M-DFT 604 (denoted byD_(M)) to generate the head 612 and tail 614 portions in time at theoutput N-IDFT 606 (denoted by F_(N) ^(H) where (⋅)^(H) is the Hermitianoperation and F_(N) is the N-DFT). Without any special design on thereference symbols, if the CP 611 of duration G is less than the tail 614of duration T, the indicated portions may become approximately identicaland may be considered to be an extended CP duration.

For example looking at the Frame 630 of the resulting time domainsignal, the Extended CP 620 of length G_(e) may have the concatenationof the tail of a previous symbol 631 _(i−1) and the CP and head portionsof the current symbol 631 _(i). Although this approach seems to achievethe goal of virtual/extended CP 620, the receiver (RX) may sufferbecause the RX DFT window 621 size changes from N to N+G, therefore, thereceiver structure may be affected for the sake of the extended CPreception, which may not be desirable. The receiver may also sufferbecause the transition between the tail of a current symbol 631 _(i) andthe CP of a next symbol 631 _(i+1) may not be continuous without anyspecial design; therefore, the data symbols, such as 613, may beinterfered. Thus, the receiver may need to perform extra operations torecover the data, which may not be ideal.

FIG. 7 illustrates an example of a perturbation approach. In thisapproach, each OFDM symbol may be perturbated to achieve continuitybetween the adjacent symbols by some perturbation vector (i.e., whichalso achieves CP extension). The transmitter diagram 701 andcorresponding time domain signal 730 of the proposed approach isillustrated on the left and right, respectively, in the example shown inFIG. 7. As with other transmission processes discussed herein, data mayenter an IDFT block (denoted by F_(N) ^(H)) 716 resulting in a symbol oflength N. A symbol may go through a Pertrubation Vector Generator block722, and/or a delay may be introduced in block 720. CP may be added atblock 708 resulting in a symbol of length N+G.

The resulting signal 730 may have a previous symbol 731 _(i−1), acurrent symbol 731 _(i), and a next symbol 731 _(i+1) for illustrationpurposes. Note that each portion of any given symbol shown in the timedomain signal 730 may be shaded with a pattern to indicate similarity.Further, there are also three TX IDFT {tilde over (X)}_(i−1), {tildeover (X)}_(i), {tilde over (X)}_(i+1) for each symbol, respectively.b_(i) may be a portion of the unperturbed signal X_(i) to bemanipulated. Element 760 may be the output of the perturbation vectorgenerator which replaces b_(i) with a_(i−1). The head of a previousperturbated OFDM symbol may be denoted as a_(i−1) at 731 a. To maintainthe continuity between the previous (i.e., TX IDFT {tilde over(X)}_(i−1)) and the current symbol (TX IDFT {tilde over (X)}_(i)), thehead of the CP of the current, or ith, perturbated OFDM symbol may alsobe a_(i−1) as shown at 731 b. Since the CP is a replica of the lastportion of the symbol TX IDFT {tilde over (X)}_(i), the vector {tildeover (X)}_(i) may include a_(i−1) at the tail corresponding location at731 bc. To this end, the IDFT 706 output, (i.e., X_(i)), may beperturbated as a function of a_(i−1) of the i+1^(th) perturbated OFDMsymbol.

This approach may work for any CP duration size, but may also presentsome issues. One issue may be that it is a dynamic method (i.e., theperturbation is a function of data) and therefore it may need to becalculated for each individual OFDM symbol, which can be processingintensive. Also, since it is a dynamic method, it may not be compatiblefor reference signals (RSs). Another issue may be that the perturbationsignal may not be used as a RS. Another issue may be that theperturbation vector follows an arbitrary structure, and hence thereceiver may need to perform an extra operation to remove the impact ofinterference due to the perturbation vector.

FIG. 8 illustrates an example of a dynamic approach for DFT-s-OFDM. Theexample transmitter diagram 801 and the corresponding time domain signal830 can be seen on the left and right of the figure, respectively. Inthis approach, the single carrier structure of DFT-s-OFDM may beexploited and the CP extension may be achieved by shifting the locationof data symbols and reusing them in the previous and next DFT-s-OFDMsymbols based on a certain rule for certain CP length and DFT-spreadsizes. As with other transmission processes discussed herein, thetransmitter diagram 801 carries out a process involving blocks D_(M)(DFT) 802, M_(f) 804, F_(N) ^(H) (IDFT) 806, and CP 808, in that order.M_(f) 804 may be a subcarrier mapping operation that maps the output ofD_(M) 802 to the inputs of F_(N) ^(H) 806. In this approach, the symbolat the input of DFT-s-OFDM block 802 s_(k) may be ordered as follows:

$s_{k} = \begin{bmatrix}a_{k}^{T} & x_{k}^{T} & b_{k - 1}^{T} & a_{k - 1}^{T} & y_{k}^{T} & b_{k}^{T}\end{bmatrix}^{T}$

where a_(k) ∈

^(M) ^(h) ^(×1), b_(k) ∈

^(M) ^(t) ^(×1), and y_(x) ∈

^(M) ^(h) ^(×1) are the data symbols, k is the DFT-s-OFDM symbol index,and the CP length should be set to

$G = {N \times {\frac{M_{h} + M_{d2} + M_{t}}{M}.}}$

In the resulting time domain signal 830, there may be a previous symbol831 _(i−1), a current symbol 831 _(i), and a next symbol 831 _(i+1) forillustration purposes. Note that each portion of any given symbol shownin the time domain signal 830 may be shaded with a pattern to indicatesimilarity. For the example shown, if a_(k) where k=2 for symbol 831_(i), then b_(k−1) is b₁ and so on for the other inputs at the beginningof the transmitter diagram 801. It may follow then that for each elementin a symbol there is a corresponding input, such as f sub a₂ is the head(H) of the current symbol 831 _(i) still using the example where k=2. Asshown, this method may achieve the Extended CP 833 which shows a CPlength (G) plus the Tail (T) and the (H) result in G_(e) which is takenfrom the other end 832 (note the similar patterns in the extended CP 833and the other end 832); this may be achieved without any complexoperation both at the transmitter and receiver, nevertheless, it mayalso introduce an undesirable constraint on the CP size G. Therefore,this approach may only be compatible with certain numerologies. Anotherpossible issue of this approach may be generating the CP extension basedon data symbols. Hence, this approach may only be compatible withcertain PT-RS structures.

FIG. 9 illustrates an example of a static approach for DFT-s-OFDM. Theexample transmitter diagram 901 and the corresponding time domain signal930 can be seen on the left and right of the figure, respectively. Aswith other transmission processes discussed herein, the transmitterdiagram 801 carries out a process involving blocks D_(M) (DFT) 902,M_(f) 904, and F_(N) ^(H) (IDFT) 906, in that order. In this approach,the single carrier structure of DFT-s-OFDM may be exploited and the CPextension shown in the signal diagram 901 may be achieved with a CPblock in the transmitter by replacing the input data symbol with fixedRSs as a_(k)=a ∈

^(M) ^(h) ^(×1), b_(k)=b ∈

^(M) ^(t) ^(×1).

In the resulting time domain signal 830, there may be a previous symbol931 _(i−1), a current symbol 931 _(i), and a next symbol 931 _(i+1) forillustration purposes. Note that each portion of any given symbol shownin the time domain signal 930 may be shaded with a pattern to indicatesimilarity. Just as in the example shown in FIG. 8, this method mayachieve the Extended CP 933 which shows a CP length (G) plus the Tail(T) and the (H) result in G_(e) which is taken from the other end 932(note the similar patterns in the extended CP 933 and the other end932). While this static method addresses the PT-RS design, it may havethe disadvantage of the dynamic method, such as where the CP lengthshould be set to

${G = {N \times \frac{M_{h} + M_{d2} + M_{t}}{M}}}.$

FIG. 10 illustrates an example of how PT-RS frequency density (K) maywork with different bandwidth schedules. Specifically, the PT-RSfrequency density may be based on the number of scheduled RBs when RBoffset is ‘0’ (i.e., starting from the first RB scheduled) and thefollowing thresholds are configured: {PT-RSthRB0=2, PT-RSthRB1=6,PT-RSthRB2=12, PT-RSthRB3=16}. RB Index 1001 on the bottom shows whatnumber RB the PT-RS 1010 is in for any given configuration. There arethree example scenarios with different PT-RS densities shown: Every RB1010 (i.e., K=1); Every 2^(nd) RB 1020 (i.e., K=2); and Every 4^(th) RB1030 (i.e., K=4). The PT-RS frequency density may not be linearlyincreased as the number of scheduled RB becomes larger. Also, the PT-RSfrequency density may be different based on the RB offset. For example,the total number of PT-RS may be different for a WTRU with RB offset=0and another WTRU with RB offset=1 although the number of scheduled RBsfor both WTRUs may be the same.

An RB offset (e.g., the starting RB index) may be used to randomize thePT-RS interference (e.g., due to collisions between PT-RSs) fromco-scheduled WTRUs. The RB offset may be determined based on one or moreWTRU-specific parameters. One such parameter may be a WTRU-ID (e.g.,temporary C-RNTI, C-RNTI, IMSI) where one or more WTRU-ID may be used.For example, when a WTRU is in RRC idle mode, the IMSI may be used asthe WTRU-ID and the C-RNTI may be used when a WTRU is in RRC connectedmode. The Temporary C-RNTI may be used to determine RB offset for RACHmsg 2, 3, and/or 4 transmission/reception and C-RNTI may be used afterthe WTRU received C-RNTI configuration.

The RB offset may also/alternatively be determined based on theWTRU-specific parameter of scrambling ID (e.g., scrambling ID configuredor indicated for DM-RS) where the scrambling ID may be configured in aWTRU-specific RRC signaling or indicated in an associated DCI for PDSCHor PUSCH scheduling.

The RB offset may also/alternatively be determined based on theWTRU-specific parameter of cell-ID (e.g., physical cell-ID) where aphysical cell-ID which may be determined during initial access procedureor detected from a synchronization signal (SS).

The RB offset may also/alternatively be determined based on theWTRU-specific parameter of an SS block time index (e.g., SS/PBCH blockindex) where the SS block index may be determined during initial accessprocedures; as discussed herein, SS block index, SS block time index,SS/PBCH block index, SS/PBCH block time index may be usedinterchangeably.

The RB offset may also/alternatively be determined based on theWTRU-specific parameter of bandwidth part (BWP) index, such as where aWTRU may be configured with one or more BWPs and a subset of configuredBWPs may be active at a time. The active BWP index on which a WTRU maybe configured or indicated to transmit and/or receive PDSCH or PUSCH maybe used to determine the RB offset value. As discussed herein, BWP andcarrier may be interchangeably used.

A default RB offset may be used before RRC connection setup, or before aWTRU may be configured with a WTRU-specific parameter. The default RBoffset may be determined by at least one of the following: a fixed RBoffset (e.g., RB offset=0); and/or, a RB offset determined based on oneor more cell-specific parameters (e.g., physical cell-ID).

In order to determine an RB offset value, a maximum RB offset value maybe determined, used, configured, or predefined. For example, if aWTRU-ID is used for RB offset value determination, a modulo (mod)operation of WTRU-ID with a maximum RB offset value (max_RB_offset) maybe used (mod stands for the modulus after division). As discussedherein, a modulo operation results in the remainder, where the modulooperation with A and B is where A may be the dividend and B may bedivisor and interchangeably expressed as A mod B, (A) mod B, and/or mod(A, B).

For example, the RB offset value=(n_(RNTI)) mod max_RB_offset, wheren_(RNTI) may be C-RNTI or temporary C-RNTI, or alternatively, n_(RNTI)may be the most significant bit (MSB) or the least significant bit (LSB)of C-RNTI or temporary C-RNTI. In either case, the max_RB_offset may bea maximum RB offset value. In some cases the max_RB_offset value may beimplicitly determined based on one or more of the following: scheduledBW (e.g., number of RBs scheduled); PT-RS frequency density (e.g., PT-RSlocated in every K RBs), where K may be interchangeably used withK_(PTRS) ^(step) as discussed herein; and/or WTRU-specific parameters.In some cases the max_RB_offset value, which may be determinedimplicitly, may be overridden by a higher layer configured max_RB_offsetvalue.

The RB offset value may be limited to a set of RB offsets that may beconfigured, determined, or used. Further, a subset of the set of RBoffsets may be determined or used based on at least one of scheduled BW,frequency density, and/or WTRU-specific parameters. The RB offset may belimited to a set/subset and determined and/or configured in one or moremethods as discussed herein.

In one method, a RB offset set may be defined, determined, or used basedon the max_RB_offset value. For example, an RB offset set may be {0, 1,. . . , max_RB_offset} which would constitute the full set of possiblevalues. In one instance, the max_RB_offset may be the frequency densityK, where max_RB_offset=K, which would make the RB offset set {0, 1, . .. , K}.

In another method, a set and/or subset of the RB offset may bedetermined based on the scheduled bandwidth N_(RB) and PT-RS frequencydensity K. In one example, a first subset may be {0} if a firstcondition is met where the first condition is (N_(RB)+1) mod K=0. Inanother example, a second subset {0, 1} may be used if a secondcondition is met, where the second condition is (N_(RB)+2) mod K=0. Inanother example, a set (i.e., full) of RB offset {0, 1, . . . ,max_RB_offset}) may be used if a third condition is met, where the thirdcondition is (N_(RB)) mod K=0.

In another method, the RB offset value may be determined based on the RBoffset value=(n_(RNTI)) mod max_RB_offset_S, where max_RB_offset_S maybe the number of RB offset values within a subset.

In another method, a subset of the RB offset set may be configured viahigher layer signaling. For example, a bitmap may be used to indicatethe subset of RB offset values.

In another approach for limiting the RB offset value, the max_RB_offsetvalue for the RB offset set, where the RB offset set is the full set ofvalues {0, 1, . . . , max_RB_offset}, may be determined based on thenumber of RBs that do not contain PT-RSs after the last RB containing aPT-RS where the RB offset=0. For example, referring back to FIG. 10, inscenario 1030 there are 16 RBs scheduled where the max_RB_offset valuemay be 3 since all of the RBs after the last RB 12 (i.e., RBs 13, 14,and 15) do not contain PT-RSs. In another example shown in scenario1030, when 15 RBs are scheduled the max_RB_offset value may be 2 sincethat is the number RBs after the 12th RB, RB 13 and 14, that do notcontain a PT-RS. In this approach, one method be where the max_RB_offsetis determined as max_RB_offset=K−N_(RB) mod K−1, where K may bedetermined based on the frequency density (e.g., where PT-RS is locatedevery K RBs) and/or N_(RB) may be number of scheduled RBs. In anothermethod, the RB offset value=(n_(RNTI)) mod max_RB_offset.

FIG. 11A shows an example of max_RB_offset value determination (orlimitation/restriction) based on scheduled RBs and PT-RS frequencydensity. Just as in FIG. 10, the shaded blocks may represent a PT-RS ina RB. In scenario 1120 there may be 8 RBs and a PT-RS in every 2nd RB(i.e., K=2): as shown in line 1121, when the offset is 0 the totalnumber of PT-RS may be 4; and as shown in line 1122, when the offset is1 the number of PT-RS may still be 4. Note, that in scenario 1120 thePT-RS density divides evenly into the number of scheduled RBs with noremainder (i.e., N_(RB) mod K=0), which results in the max_RB_offsetbeing equal to the PT-RS density K=2; said another way, when K=2, thenthe RB offset would be the first two possible values, where the valuesstart at 0, therefore the set of values would be {0,1}. More generally,this may be written as when N_(RB) mod K=0, then max_RB_offset=K.

In scenario 1110 there may be 7 RBs and a PT-RS density of one in every2^(nd) RB (i.e., K=2). Note here that the PT-RS density does not divideevenly into the number of scheduled RBs (i.e., N_(RB) mod K≠0).Consequently, when the RB offset is 0 the total number of PT-RS may be 4as shown in line 1111; and when the offset is 1 the total PT-RSdecreases to 3 (i.e., the RB offset value has limited the number ofPT-RS).

In some cases, the number of PT-RS for a scheduled bandwidth wouldpreferably be the same to avoid performance degradation for a WTRU.Therefore, situations where a different number of PT-RSs exist for thesame scheduled bandwidth as shown in the line 1112 may want to beavoided. In order to ensure the number of PT-RS stays the same, the fullpossible set of RB offset values, max_RB_offset, may need to be limited.For example, where the RB offset may be based on the WTRU-ID asdiscussed herein (i.e., n_(RNTI) mod max_RB_offset), limiting themax_RB_offset may enable the ability to keep the number of PT-RS thesame for a given number of scheduled RBs. As shown with scenario 1120,limiting the max_RB_offset may only be necessary when the PT-RS densitydoes not divide evenly into the number of scheduled RBs (i.e., N_(RB)mod K≠0). In the scenario of 1110, the max_RB_offset may be limited to afunction of the PT-RS density and the number of scheduled RBs;specifically, the max_RB_offset may be limited to the remainder of thePT-RS density divided into the number of scheduled RBs, which would be 7mod 2, which equal 1. As discussed above, a numerical value formax_RB_offset, such as 1, results in a limited set (i.e., subset) of RBoffset values, where any RB offset value starts at 0. It follows then,if max_RB_offset is limited to 1, then the subset of max_RB_offset wouldbe {0}, meaning, that any RB offset greater than 0, such as shown inline 1112 with RB offset values {0,1}, would result in having adifferent number of total PT-RSs. More generally, this may be written aswhen N_(RB) mod K≠0, then max_RB_offset=N_(RB) mod K.

FIG. 11B illustrates an example process of sending a PT-RS transmissionto ensure the PT-RS density K remains the same to address possibleissues discussed with regard to FIG. 11A. In a first step 1151 the PT-RSdensity K and the number of scheduled RBs N_(RB) may be determined. Inone case, a device, such as a WTRU, may have a certain bandwidthscheduled (i.e., control information is received on a control channel).The WTRU may determine the PT-RS density K based on the scheduledbandwidth. If At step 1152, if PT-RS density K divides evenly into thenumber of scheduled RBs N_(RB), then at step 1152 the max_RB_offset maybe equal to the PT-RS density, or if it does not, then the max_RB_offsetmay be a function of the PT-RS density and the number of scheduled RBs.At step 1154, the RB offset value may be determined depending on theresult of step 1153. At step 1155, once the RB offset is determined,this information can be used to transmit and/or receive a transmissionwith PT-RS.

In another approach for limiting the RB offset value, if themax_RB_offset value is smaller than K, there may be one or more methodsthat apply to randomize interference with a restricted/limited set of RBoffset values. There may be one or methods that can follow thisapproach.

In one method an RE location, or a subframe location, of a PT-RS withina RB may be determined based on one or more WTRU-specific parameters.For example, when the RB offset values are restricted/limited the RElocation of a PT-RS within an RB may be determined on WTRU-specificparameters, and when the RB offset values are not restricted/limited(e.g., max_RB_offset=K), an RE location of a PT-RS within an RB may bedetermined based on non-WTRU-specific parameters (e.g., fixed,predefined, cell-specific parameters).

In another method, a PT-RS scrambling sequence may be determined basedon one or more WTRU-specific parameters. For example, a PT-RS scramblingsequence may be initialized based on non-WTRU-specific parameters whenthe RB offset values are not restricted and the PT-RS scramblingsequence may be initialized based on one or more WTRU-specificparameters when the RB offset values are restricted.

In another method, a PT-RS time location (e.g., start symbol index) maybe determined based on one or more WTRU-specific parameters. Forexample, a first symbol index may be used as a starting symbol for PT-RStransmission when the RB offset values are not restricted, and a secondsymbol index may be used as a starting symbol for PT-RS transmissionwhen the RB offset values are restricted. The first symbol index may befixed, configured, and/or predefined and the second symbol index may bedetermined based on one or more WTRU-specific parameters.

FIG. 12 illustrates an example of cyclic shifting RBs containing PT-RS.In this approach a RB offset set may be defined, determined, or usedwith set {0, 1, . . . , max_RB_offset} where the max_RB_offset may be K(e.g., the PT-RS density); the RBs that contain PT-RS may be cyclicallyshifted based on the RB offset value. Therefore, the number of RBscontaining PT-RS may be the same irrespective of the RB offset value.Scenario 1210 shows several instances of slots with 7 RBs with a PT-RSin every 2nd RB. In one instance 1211 the RBs containing PT-RS may beevenly distributed where the RB offset is 0, which results in a PT-RSdensity of 4. In another instance 1212 the RB offset may be 1 and theRBs containing PT-RS may not be evenly distributed where one PT-RS RB1202 has been shifted and is adjacent to another PT-RS RB but the PT-RSdensity is still 4. Additionally, the cyclic shift value may bedetermined based on one or more WTRU-specific parameters. For example,the PT-RS not assigned to a RB due to RB offset value may be located inone of the RBs not containing PT-RS, wherein the RB location may bedetermined based on a WTRU-ID (e.g., C-RNTI).

In some cases, the reference locations of RBs containing PT-RS may bebased on RB offset=0, where the number of RBs containing PT-RS may bethe same as the case of RB offset=0 irrespective of the RB offset valuedetermined and where the PT-RS density may be 4.

In one approach, power boosting PT-RS may be used when the number of RBsused for PT-RS for an RB offset is smaller than that for a reference RBoffset. For example, a reference RB offset may be defined, configured,or used with RB offset=0 and the number of RBs used for PT-RS may beK_(p) when RB offset=0. If the number of RBs used for PT-RS for acertain RB offset is smaller than K_(p), power boosting of PT-RS may beused. In this approach, a first power level may be used for PT-RS whenthe number of RBs containing PT-RS is the same as K_(p) for a first RBoffset value; a second power level (e.g., higher than the first powerlevel) may be used for PT-RS when the number of RBs containing PT-RS issmaller than K_(p) for a second RB offset value. The second power levelmay be determined based on the ratio between the number of RBscontaining PT-RS for a certain RB offset value and K_(p).

Also in this approach constellation points may be correlated to theoffset value, first constellation points (e.g., QPSK constellation) maybe used for the PT-RS sequence when the number of RBs containing PT-RSis the same as K_(p) for a first RB offset value; second constellationpoints (e.g., outermost constellation points of 16QAM, 64QAM, or 256QAM)may be used when the number of RBs containing PT-RS is smaller thanK_(p) for a second RB offset value. The modulation order (e.g., 16QAM,64QAM, or 256QAM) for outermost constellation points may be determinedbased on the ratio between the number of RBs containing PT-RS for acertain RB offset value (K_(a)) and K_(p). For example, a firstmodulation order (e.g., 16QAM) may be used if K_(a)/K_(p) is larger thana predefined threshold; a second modulation order (e.g., 64QAM) may beused if K_(a)/K_(p) is less than the predefined threshold. Themodulation order for the outermost constellation points may bedetermined based on the modulation order indicated, determined, orscheduled for the associated data channel (e.g., PDSCH or PUSCH).

In one scenario, RB offset values may be used to shift the PT-RS from adefault RB location to a different RB, such as a fixed number of RB awayfrom the default RB location, to avoid a source of intra or inter cellinterference from other transmitters of PT-RS in the same RB location.If significant PT-RS based interference is present, the time andfrequency of the PT-RS density may be modified or changed to avoid orreduce the interference level. For example, the following Table 4illustrates the combinations of RB offset and PT-RS frequency densitypossible assuming both transmitters use PT-RS time density=1 (e.g.,PT-RS transmitted every symbol).

TABLE 4 An example of PT-RS time/frequency density based on RB offsetPT-RS Frequency Density Interfering PT-RS Serving PT-RS RB Offset 1 1 01 2 0 1 4 0 2 1 0 2 2 1 2 4 1 4 1 0 4 2 1 or 3 4 4 1, 2, or 3

For this scenario, the frequency density of one or more interferencesources (e.g., co-scheduled WTRU or neighbor cell) may be indicated to aWTRU via higher layer signaling or L1 signaling (e.g., DCI). For thisindication to the WTRU, one or more approaches may be applicable.

In one approach, a WTRU may receive the frequency density of aninterfering PT-RS in an associated DCI for data scheduling and the PT-RSdensity (e.g., serving PT-RS time and/or frequency density) for the WTRUmay be determined based on the frequency density of the interferingPT-RS. If the interfering PT-RS density is increased, the serving PT-RSdensity may also be increased. Alternatively, if the interfering PT-RSdensity is increased, the serving PT-RS density may be decreased.

In another approach, a set of RB offset values may be limited based onthe interfering PT-RS density. For example, a smaller set of RB offsetvalues may be used if the interfering PT-RS density is lower and alarger set of RB offset values may be used if the interfering PT-RSdensity is higher. In a further example, if an interfering PT-RS densityis low (e.g., 1), a first subset of RB offset values (e.g., {0}) may beused and if an interfering PT-RS density is medium (e.g., 2), a secondsubset of RB offset values (e.g., {0, 1}) may be used; if an interferingPT-RS density is high (e.g., 4), a third subset of RB offset values(e.g., {0, 1, 2, 3}) may be used.

In another approach, a set of RB offset values may be limited based onan interfering PT-RS density and a serving PT-RS density.

Similar options for RB offset may be possible if either one of thetransmitters uses a PT-RS time density<1 (e.g., an OFDM symbol offset).Also, an OFDM symbol offset may be needed to handle DM-RS basedinterference to PT-RS. Another possibility is to use subcarrier offsetsfor PT-RS within a RB.

FIG. 13 illustrates an example of a PT-RS mapping for 7 RB withdifferent RB offset values. In this approach, an RB offset may bedetermined based on a C-RNTI and/or a subframe/slot number or index. Forperspective, referring back to FIG. 2 for the PT-RS mapping withdifferent PT-RS densities of K_(PTRS) ^(step)=1, 2, and 4 RBs was shown;since there was a PT-RS in the starting scheduled RB location the RBoffset may be assumed to be 0 since there is a PT-RS RB in the firstindex. Therefore, for any configuration where rem(N_(RB)/K_(PTRS)^(step))≠0, the PT-RS density per slot may vary based on the RB offsetvalue. Now looking at the examples shown in FIG. 13, there are PT-RSmappings for each for N_(RB)=7 RBs each with different RB offset valuesof 0 RB in scenario 1310 and 1 RB in scenario 1320. For scenario 1310there is a RB every 2^(nd) RB and the RB offset may be 0, which mayresults in a PT-RS density of 4; for scenario 1320 there is a RB every2^(nd) RB and the RB offset may be 1, which may result in a PT-RSdensity of 3. As demonstrated, in the configuration with RB offset=1,the overall number of PT-RS will become less than the case when RBoffset=0, which may lead to some performance degradation.

FIG. 14 illustrates an example of a PT-RS mapping with different RBwidths of schedules. In a scenario 1410 there may be 7 RBs with a PT-RSevery 2^(nd) RB resulting in a density of 4. In scenario 1420 there maybe 13 RBs with a PT-RS every 4th RB resulting in a density of 4; such aconfiguration may have even more impact on the performance since thescheduling is so spread out.

FIG. 15 illustrates an example PT-RS mapping for 7 dynamic RB offsetvalues. In this approach the RB offset value may be adjusted ordetermined dynamically based on a time index to have an equal average ofPT-RS over the duration of the transmission. For the scenario 1510,there may be 7 RBs with a PT-RS every 2^(nd) RB. The time index may beat least one of frame number (n_(Frame)), slot number (n_(Slot)), orsymbol number (n_(Sym)). For example, an initial RB offset may bedetermined based on the C-RNTI, and then an additional RB offset may beapplied based on the n_(Slot) where n_(Slot) is the slot numbercorresponding to the current transmission. Scenario 1510 shows anexemplary implementation based on setting the offset value based onoff/even slot number that results in each increment in slot (i.e., slotn, slot n+1, slot n+2, . . . slot n+k) alternating the RB offset valuewhich also effects the PT-RS density (i.e., the density alternatingbetween 4 and 3, based on an offset value of 0 and 1, respectively). Theslot number may be a slot number within a radio frame or an absolutenumber. In an alternative example, the RB offset value may jointly bedefined based on the C-RNTI and a time index or the like. In anotherexample, the RB offset adjustment may be applied only to theconfigurations that exhibit unequal distribution, or universally appliedon all configurations regardless of the impact of the offset value.

FIG. 16 illustrates an example of PT-RS mapping for 13 RBs per slot andwith dynamic RB offset values. In this case, the RB offset value may beadjusted dynamically based on a time index to counter the impact offrequency selective fading. As such, regardless of the impact of thePT-RS density, the RB offset may be dynamically changed for allconfigurations to avoid experiencing long fading. The scenario 1610shows 13 RBs for each slot with every 4th a PT-RS RB (i.e., whereK_(PTRS) ^(step)=4). The time index may be based on n_(Frame), K_(PTRS)^(step), n_(Slot), or n_(Sym), etc., or a combination there of. Forexample, an initial RB offset may be determined based on the C-RNTI, andthen an additional RB offset may be applied to shift the location of thePT-RS RB per slot or based on slot number. The RB offset may bedetermined based on n_(Slot) and K_(PTRS) ^(step), where the additionaloffset may be defined as rem(n_(Slot)/K_(PTRS) ^(step)). As shown, theRB offset increases with each slot number: so slot n the RB offset is 0,slot n+1 the offset is 1, slot n+2 the RB offset is 2, and slot n+3 theRB offset is 3. Note that once the RB offset is 3, in the next slot,n+4, the RB offset would go back to 0 since the PT-RS density is only 4and you cannot have an RB offset of 4 without having a PT-RS density ofat least 5, which is not envisioned in this example.

In an embodiment, the PT-RS density may be dependent on frequencyresource allocation type. Modulated information symbols may sometimes bemapped to time and frequency resources before transmission. Multipleinformation symbols may be mapped to discrete, contiguous time andfrequency blocks. In LTE and NR, a modulated information symbol may bemapped to a time and frequency unit called a Resource Element (RE). A REmay comprise one subcarrier in one OFDM symbol. A block REs including 12contiguous subcarrier (i.e., in frequency) by 7 OFDM symbols (i.e., aslot may comprise a RB). When individual, or multiple RBs are mappedcontiguously or non-contiguously in time and frequency, they areconsidered to have a localized or distributed resource allocation type,respectively. Since PT-RS may be mapped within allocated RBs that canhave a localized or distributed resource allocation type, PT-RS densityin time and frequency may be dependent upon that type. Therefore, in atleast some circumstances there is a need to make PT-RS time andfrequency density also dependent upon whether localized or distributedresource allocation type is used.

FIG. 17 illustrates an example of PT-RS frequency location based onsymbol location. Just as in FIG. 2, the horizontal axis 1704 is symbols(i.e., OFDM) and the vertical axis 1705 is subcarriers. Regardless ofwhether the NR resource allocation types 0 and 1 indicate that alocalized or distributed allocation is required, PT-RS time andfrequency densities may be maintained. If RBs are distributed in timeduring a transmission interval, the PT-RS time density, which may insome cases apply for a localized allocation, may apply to each timeregion separately as shown in FIG. 17. If RBs are distributed infrequency during a transmission interval, the PT-RS frequency density,which may in some cases apply for a localized allocation, may apply toeach frequency region of continuously allocated resource blocks or aResource Block Group (RBG) separately (i.e., for the carrier bandwidthpart used). For example 1701 there may be a PT-RS every symbol whichdoes not exhibit any change. For example 1702 there may be a PT-RSdensity of every other symbol (i.e., every 2^(nd) symbol), which mayrestart when the frequency changes due to a different frequency regionbeginning at the halfway 1712. For example 1703, there may be a PT-RSsymbol every 4th symbol, which may restart when the frequency changesdue to a different frequency region beginning at the halfway 1713.

FIG. 18 illustrates an example of PT-RS frequency density based on RBG.The frequency density may be determined based on RBG size that has beenconfigured or determined, and for each scenario of FIG. 18 there may bea different RBG. In scenario 1810, there may be a PT-RS every RB with adensity of every RB. For Scenario 1820 there may be a different RBG witha different density of every 2^(nd) RB. For scenario 1830, there mayagain be a different RBG with a different density of every 4th RB.

In an embodiment, the RE location (e.g. subcarrier location, RE offset)of PT-RS within a RB containing PT-RS may be determined based on atleast one of the physical cell-ID, WTRU-ID (e.g., C-RNTI, temporaryC-RNTI, or IMSI), frequency density of PT-RS, time density of PT-RS, andmax_RB_offset value. For example, if the max_RB_offset value is a firstvalue (e.g., 0), the RE location (or RE offset) may be determined basedon the WTRU-ID and if the max_RB_offset value is a second value(e.g., >0), the RE location (or RE offset) may be determined based oncell-ID. Alternatively, if the max_RB_offset value is a first value, theRE location (or RE offset) may be determined based on frequency densityof PT-RS and if the max_RB_offset value is a second value, the RElocation (or RE offset) may be determined based on cell-ID.

FIG. 19 illustrates an example of PT-RS generation for of π/2-BPSK datamodulation. For binary phase shift keying (BPSK) modulation 1912, bitsequence b(n) may be mapped to a complex-valued modulation symbol xbased on

$x = {\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{b(n)}}} \right) + {j\left( {1 - {2{b(n)}}} \right)}} \right\rbrack}$

In case of π/2-BPSK modulation 1914, bit sequence b(n), where n is theindex (i.e., location), may be mapped to a complex-valued modulationsymbol x based on

$x = {e^{jn{\pi/2}}{\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{b(n)}}} \right) + {j\left( {1 - {2{b(n)}}} \right)}} \right\rbrack}}$

where j=√{square root over (−1)}.

As discussed herein, π and pi may be interchangeably used. As seen inFIG. 19, there may be a PT-RS sequence design where the modulation orderfor the associated data (e.g., PDSCH or PUSCH) may be pi/2 BPSK. PT-RSbits consisting of zeros and ones may be multiplexed 1910 with data bitsaccording to a predefined pattern. The resulting multiplexed bits b 1902may go through BPSK modulation 1912 resulting in d 1904 and then pi/2modulation 1914 resulting in c 1906. Decoupling the BPSK and pi/2modulations may be beneficial if an orthogonal cover code (OCC) is to beapplied over the PT-RS bits. After the pi/2 modulation 1914, theresultant symbols may be processed by a DFT block 1916 and an optionalfrequency domain spectral shaping (FDSS) 1918, which may be implementedeither after or before the DFT 1916. Then, the shaped symbols may bemapped 1920 to the allocated subcarriers, and go through IDFT processingblock 1922 to be ready for transmission in an OFDM symbol.

FIG. 19 may be further elaborated with the following example: assumethat the DFT size is set to N=12 (e.g., total number of data and PT-RSbits) due to the allocated resources and that the PT-RS bits will beinserted in two chunks at the head and tail of a sequence b 1902, andthat each chunk consists of 2 bits; then, the multiplexed vector of dataand PT-RS bits 1910 may be written as b=[X, X, 8 data bits, Y, Y] whereX, Y, and data bits are either 0 or 1. Note, that in general the PT-RSbits in each chunk do not have to be the same, so in this example itcould be values X1, X2, Y1, and Y2, where there are different X valuesand Y values. For the sake of illustration, there may be values forb=[1, 1, 0, 0, 1, 1, 0, 1, 0, 1, 1 1] and after BPSK modulation 1912 ofb 1902, the modulated sequence may become d 1904 as shown in Table 5below, where the following notation is used: 1i=√{square root over(−1)}.

TABLE 5 Example of data and PT-RS bits after BPSK modulation −0.7071 −0.7071i −0.7071 − 0.7071i   0.7071 + 0.7071i   0.7071 + 0.7071i −0.7071− 0.7071i −0.7071 − 0.7071i   0.7071 + 0.7071i −0.7071 − 0.7071i  0.7071 + 0.7071i −0.7071 − 0.7071i −0.7071 − 0.7071i −0.7071 − 0.7071i

Then, the sequence d 1904 is multiplied element-to-element (Hadamardproduct) with the vector

${{p(n)} = e^{{(\frac{j\pi}{2})}n}},{n = 0},\ldots\mspace{14mu},{N - 1}$

to perform pi/2 modulation 1914 resulting in c 1906. Note, that p(n) maybe written slightly differently, so long as it represents the pi/2modulation. An example of the calculated values for p(n) is given inTable 6 below.

TABLE 6 Example of p(n)   1.0000 + 0.0000i   0.0000 + 1.0000i −1.0000 +0.0000i −0.0000 − 1.0000i   1.0000 − 0.0000i   0.0000 + 1.0000i−1.0000 + 0.0000i −0.0000 − 1.0000i   1.0000 − 0.0000i   0.0000 +1.0000i −1.0000 + 0.0000i −0.0000 − 1.0000i

Then, we get c=d∘p as shown in Table 7 below.

TABLE 7 Example of pi/2 BPSK modulated PT-RS/data bits −0.7071 − 0.7071i  0.7071 − 0.7071i −0.7071 − 0.7071i   0.7071 − 0.7071i −0.7071 −0.7071i   0.7071 − 0.7071i −0.7071 − 0.7071i −0.7071 + 0.7071i  0.7071 + 0.7071i   0.7071 − 0.7071i   0.7071 + 0.7071i −0.7071 +0.7071i

FIG. 20 illustrates an example of PT-RS generation for pi/2 BPSK datamodulation and OCC. As discussed herein, some elements may beinterpreted to be similar if they use the same last two digits, such asin FIG. 19 and FIG. 20. Further, FIG. 20 may be similar to FIG. 19 butfor when the PT-RS bits are transmitted in chunks, an orthogonal covercode (OCC) may be applied over the PT-RS bits within the chunk. Notethat the bits which are multiplied by the OCC may be the same. In such ascenario, the OCC may be applied to the PT-RS bits after the BPSKmodulation 2012 but before the pi/2 modulation 2013 (i.e., on thesequenced 2004) resulting in OCC'd PT-RS bits e 2005 (i.e., vector e).Note that applying the OCC after the pi/2 modulation may destroy thephase continuity of the signal and result in a signal with a larger peakto average power ratio.

To further elaborate, assume for an example that the chunk size is 2 andthe OCCs to be applied are [1 1] and [1 −1]. The two PT-RS bits in eachchunk in d 2004 may be multiplied with one of these OCCs 2013.Continuing with the example if the OCC is [1 1], then the vector e 2005will be as shown in Table 8 below.

TABLE 8 Example of applying [1 1] OCC on PT-RS bits after BPSKmodulation (−0.7071 − 0.7071i) × 1 (−0.7071 − 0.7071i) × 1   0.7071 +0.7071i   0.7071 + 0.7071i −0.7071 − 0.7071i −0.7071 − 0.7071i  0.7071 + 0.7071i −0.7071 − 0.7071i   0.7071 + 0.7071i −0.7071 −0.7071i (−0.7071 − 0.7071i) × 1 (−0.7071 − 0.7071i) × 1

If the OCC is [1 −1], then the vector e 2005 will be as shown in Table 9below.

TABLE 9 Example of applying [1 −1] OCC on PT-RS bits after BPSKmodulation (−0.7071 − 0.7071i) × 1   (−0.7071 − 0.7071i) × −1   0.7071 +0.7071i   0.7071 + 0.7071i −0.7071 − 0.7071i −0.7071 − 0.7071i  0.7071 + 0.7071i −0.7071 − 0.7071i   0.7071 + 0.7071i −0.7071 −0.7071i (−0.7071 − 0.7071i) × 1   (−0.7071 − 0.7071i) × −1

The OCCs applied to each chunk of PT-RS bits by a given WTRU may be thesame for all chunks or different for one or more chunks. As an example,with two chunks and two bits, the OCC codes applied by a WTRU may be {[11], [1 1} or {[1 −1], [1 −1]}, or {[1 1], [1 −1], or {[1 −1], [1 1]}.

If the same OCC is applied over all chunks, the index of the code may besignaled or determined implicitly using another parameter, for examplethe WTRU ID. As an example, mod(WTRU ID, 2) may determine one of the twoOCCs while mod(WTRU ID, 4) may determine one of the four OCCs. Ingeneral, mod (WTRU ID, k) may determine one of the k OCCs.

The indices of the OCCs to be applied over the chunks may be determinedby a rule such as cycling through the codes. As an example, assume thereare 4 chunks and each chunk has 2 PT-RS bits. Then, a WTRU may apply thefollowing codes on the four chunks in the given order: {[1 1], [1 −1],[1 1], [1 −1]} or {[1 −1], [1 1], [1 −1], [1 1]}. The index of the firstcode may be signaled or determined implicitly, for example by the WTRUID.

FIG. 21 illustrates an example of cycling through OCC. The cyclingoperation may be performed clockwise 2101 or counter clock wise 2102,where the indices of the OCCs are placed on a circle. For example, OCC#1=[1 1 1 1]; OCC #2=[1 1−1 −1]; OCC #3=[1 −1 1−1]; OCC #4=[1 −1−1 1].

In one approach, OCC may be used for a reference signal sequence (e.g.,within a chunk) based on the modulation order of the reference signal(e.g., PT-RS). For example, if a first modulation order (e.g., pi/2BPSK) is used for a reference signal, OCC may not be used (e.g., OCCwith all ‘1’ entry may be used); if a second modulation order (e.g.,QPSK) is used for a reference, OCC may be used and the OCC may bedetermined based on one or more of the following: one or moreWTRU-specific parameters (e.g., WTRU-ID (e.g., C-RNTI), scrambling ID,etc.); higher layer configured parameter; layer (e.g., transmissionlayer); number of layers; one or more cell-specific parameters (e.g.,cell-ID); and/or use of a specific OCC (e.g., all ‘1’ entry) may bereferred to as no use of OCC.

Concerning common PT-RS design for all modulation types, such as QPSKmodulation, pairs of bits b(n) and b(n+1) may be mapped tocomplex-valued modulation symbols x according to

$\left. {x = {\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{b(n)}}} \right) + {j\left( {1 - {2{b\left( {n + 1} \right)}}} \right)}} \right)}} \right\rbrack$

FIG. 22 illustrates an example of pi/2 BPSK and QPSK constellation. Notethat both the pi/2 BPSK modulation described above and QPSK modulationsmay have the same constellation as shown in FIG. 22. Measured on thehorizontal axis are real numbers 2201 and on the vertical axis areimaginary numbers 2202. Given that pi/2 BPSK and QPSK have the sameconstellation, it may be desirable to have a sequence design for PT-RSthat is common for all types of data modulation including pi/2 BPSK aswell as QPSK, 16QAM, and others. This way, in general, the number ofbits required for PT-RS in one DFT-s-OFDM symbol may be equal to V*X (Vmultiplied by X) where V is the chunk size and X is the number ofchunks.

FIG. 23 illustrates a common PT-RS design sample. For this example,PT-RS bits 2310 may have values of p(0), p(1), p(2), and p(3). Onceprocessed through the BPSK Modulation 2302, the PT-RS sequence may begenerated according to

${{x(n)} = {e^{\frac{jn\pi}{2}}{\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{p(i)}}} \right) + {j\left( {1 - {2{p(i)}}} \right)}} \right\rbrack}}},{i = 0},1,{{\ldots\mspace{14mu}{VX}} - 1}$

which is shown at 2303, and n is the index of the DFT 2304 input (n=0,1, . . . , N−1) in which the i′th PT-RS bit p(i) will be inserted.

As an example, if the DFT size is 12 and the PT-RSs are inserted intothe DFT 2304 inputs n=0, 1 (Head) and n=10, 11 (Tail); then the PT-RSthat will be inserted into these DFT 2304 inputs may be written as

${{x(0)} = {e^{\frac{j0\pi}{2}}{\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{p(0)}}} \right) + {j\left( {1 - {2{p(0)}}} \right)}} \right\rbrack}}}{{x(1)} = {e^{\frac{j1\pi}{2}}{\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{p(1)}}} \right) + {j\left( {1 - {2{p(1)}}} \right)}} \right\rbrack}}}{{x\left( {10} \right)} = {e^{\frac{j10\pi}{2}}{\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{p(2)}}} \right) + {j\left( {1 - {2{p(2)}}} \right)}} \right\rbrack}}}{{x\left( {11} \right)} = {e^{\frac{j11\pi}{2}}{\frac{1}{\sqrt{2}}\left\lbrack {\left( {1 - {2{p(3)}}} \right) + {j\left( {1 - {2{p(3)}}} \right)}} \right\rbrack}}}$

FIG. 24 illustrates an example of OCC application to PT-RS design forthe lowest n in a group, and FIG. 25 illustrates the same except withthe largest n in the group. Note that as explained with regard to FIG.21, if OCC is to be applied over the PT-RS bits in a chunk and if themodulation type for data is pi/2 BPSK, then OCC may be applied afterBPSK modulation but before pi/2 modulation. The same method may also beused when the data modulation type is not pi/2 BPSK. Alternatively, whenthe data modulation type is not pi/2 BPSK, OCC may be applied over thepi/2 BPSK modulated PT-RS bits as shown in the example of FIG. 24. Alsoin FIGS. 24, O1 and O2 2405 may denote the OCC bits (e.g., [O1 O2]=[11]; or [1 −1]).

With OCC, the number of PT-RS bits 2410 required may be (X*V)/L where Lis the length of the OCC. After these bits are BPSK modulated 2402, eachbit may be repeated L times and mapped to the corresponding inputs ofthe DFT 2404. The example in FIG. 24 uses L=2. The bits in each L-sizegroup may then be multiplied with the same coefficient e^(jmπ/2) 2403where m may be determined based on the indices of the DFT 2404 inputscorresponding to the L-size group. For example, m may be the lowest n inthat group as shown in FIG. 24 (i.e., e^(jmπ/2) goes to e^(j(0)π/2) ande^(j(N−1)π/2)), or the largest n in that group as shown in FIG. 25(i.e., e^(jmπ/2) goes to e^(j(1)π/2) and e^(j(N)π/2)). The processdescribed with respect for FIG. 24 may be similar to FIG. 25 but for then value. Alternatively, m may be set to be equal to i (the PT-RS bitindex, i=0, 1, . . . , (X*K)/L).

The PT-RS bits p(i) may be generated using a pseudorandom numbergenerator, for example the Gold sequence generator used in LTE.

In one scenario, the OCC may depend on the data modulation order. Forpi/2 BPSK modulation of the data bits, a default OCC vector may beapplied over the PT-RS chunks (e.g., a vector of all the ones such as [11], or [1 1 1 1]).

If pi/2 BPSK modulation is defined as follows

$x = {e^{jn{\pi/2}}{\frac{1}{\sqrt{2}}\left\lbrack {{2{b(n)}} - 1} \right\rbrack}}$

then, the constellation becomes as shown in the example of FIG. 26,where the horizontal axis shoes Real numbers 2601 and the vertical axisshows Imaginary numbers 2602. In such a case, pi/2 BPSK modulated PT-RSmay be used when data modulation is QPSK or a higher order QAMmodulation after multiplying the PT-RS symbols by e{circumflex over( )}(jπ/4) to create a constellation as shown in FIG. 26.

In another scenario a first RS sequence may be based on pi/2 BPSK and asecond RS sequence may be a phase shifted version of the first RSsequence. In such a scenario, one or more of the following may apply: afirst RS sequence may be used when a modulation order of its associateddata channel is a first modulation order (e.g., pi/2 BPSK); and/or aphase shifted version of the first RS sequence (e.g., a second RSsequence) may be used when a modulation or its associated data channelis a second modulation order (e.g., a modulation order higher than pi/2BPSK), where the phase shift value may be predefined, preconfigured, ordetermined based on constellation of pi/2 BPSK and QPSK.

In an embodiment, PT-RS for virtual CP (i.e., extended CP) in NR may beconsidered, where waveforms and frame structure may be standardized: CPDFT-s-OFDM and CP OFDM may be waveforms in the uplink direction; pre-DFTPT-RSs may be used for DFT-s-OFDM; and, there may be multiplenumerologies that have subcarrier spacing defined as Δf=2^(μ)·15 [kHz]which is also tabulated in Table 10 below. For different subcarrierspacing, the CP size may be based on the formula given by

N_(u)^(μ) = 2048κ ⋅ 2^(−μ) $N_{{CP},l}^{\mu} = \left\{ \begin{matrix}{5\ 12{\kappa \cdot 2^{- \mu}}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{144{\kappa \cdot 2^{- \mu}}} + {16\kappa}} & {{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}},\ {l = {{0\mspace{14mu}{or}\mspace{14mu} l} = {7 \cdot 2^{\mu}}}}} \\{144{\kappa \cdot 2^{- \mu}}} & {{{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}},\ {l \neq {0\mspace{14mu}{and}\mspace{14mu} l} \neq {7 \cdot 2^{\mu}}}}\end{matrix} \right.$

TABLE 10 Example of Subcarrier spacing in NR μ Δf = 2^(μ) · 15 [kHz] 015 1 30 2 60 3 120 4 240 5 480

Based on these considerations, the CP size may reduce exponentially forlarger subcarrier spacing in NR. This means that OFDM or DFT-s-OFDMsymbols may be susceptible to multipath delay spread for highersubcarrier spacing and the receiver may suffer ISI for higher subcarrierspacing in certain cases (e.g., outdoor scenarios or cases with NLOSlinks). Existing solutions may either increase the complexity of boththe transmitter and receiver (e.g., UW and CP combination, perturbationapproach) or may not be compatible with the numerologies that are usedfor NR (i.e., dynamic method and static method for DFT-s-OFDM). Forexample, the static method, which inherently allows pre-DFT PT-RSs, maydictate the CP length to be

${G = {N \times \frac{M_{h} + M_{d2} + M_{t}}{M}}}.$

However, this may not be feasible with one or more of the possiblenumerologies for NR. Hence, it may be useful to consider virtual CPsolutions that allow CP extensions while being compatible with possibleconstraints on CP sizes, such as for NR.

FIG. 27 illustrates an example approach to generating CP extending RSsbased on predetermined RSs with a CP extender block. In this approach,CP extending RSs may be calculated based on other pre-determined RSs byusing a CP extender block 2708 and mapping to the input of DFT-s-OFDM toextend the normal CP duration. The detailed transmitter block diagramand the corresponding time domain symbols (i.e., three DFT-s-OFDMsymbols back-to-back 2731 i−1, 2731 i, and 2731 _(i+1)) for this methodmay be seen in the example diagram shown in FIG. 27. In the TX blockdiagram 2701, d ∈

^(M) ^(d) ^(×1) is the data vector that contains the data symbols, h ∈

^(M) ^(h) ^(×1) and t ∈

^(M) ^(t) ^(×1) are the vectors that may comprise predetermined RSs, orPT-RSs, and {dot over (h)} ∈

^(R) ^(h) ^(×1) and {dot over (t)} ∈

^(R) ^(t) ^(×1) are the vectors that may comprise the CP extending RSsgenerated through a CP extender block 2708. The inputs of the CPextender block may be the size of {dot over (h)} and {dot over (t)}(i.e., R_(h) and R_(t)), the amount of extension in time domain (i.e., Tand H), the pre-determined RSs, or PT-RSs (i.e., h and t) the normal CPsize G, and/or the symbol mapping matrix M_(t) ∈

^(M×M), which maps the vectors d, h, t, h, and t to the inputs ofM-point DFT matrix D_(M).

Looking at the FIG. 27, the CP extender block 2708 may generate thevector {dot over (h)} and {dot over (t)} based on a minimizationcriterion to achieve virtual CP. Since the CP extender block 2708 workson fixed values in this approach, the output of the CP extender block270 may be calculated offline and may be stored in a memory in thetransmitter (not shown). After {dot over (h)} and {dot over (t)} aregenerated, d, h, t, {dot over (h)}, and {dot over (t)} may be mapped tothe input of M-DFT via symbol mapping matrix M_(t) 2710. Then, the M-DFTof the mapped vectors d, h, t, {dot over (h)}, and {dot over (t)} may becalculated. In the following steps, D_(M) 2712 results in output of DFTof size M (M-DFT), which may be mapped to the subcarriers via frequencydomain mapping matrix denoted by M_(f) ∈

^(N×M) 2714 and the N-IDFT of the mapped output of M-DFT may becalculated by an IDFT matrix F_(N) ^(H)∈

^(N×N) 2716, which gives the time domain signal vector x ∈

^(N×1). Then, the last G samples of x prepends to the signal vector xand the resulting vector may be transmitted resulting in the time domainsignal diagram 2730.

The overall operation that generates the vector x may be expressed as

$X = {{F_{N}^{H}M_{f}D_{M}{M_{t}\begin{bmatrix}0 \\t \\h \\\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}} = {A\begin{bmatrix}0 \\t \\h \\\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}}$

where A=F_(N) ^(H)M_(f)D_(M)M_(t) ∈

^(N×M) is the waveform matrix that generates the vector x from thevector d, h, t, {dot over (h)}, and {dot over (t)}.

FIG. 28 illustrates an example of a signal structure designed to achievevirtual CP with the CP extender block. For the sake of explanation, thederivation of the CP extended portion may be based on pre-determined RSs(e.g., PT-RS). The signal structure with the CP portion G may beutilized for the sake of achieving the virtual CP shown when a datavector M_(d) is set to a zero vector. For a given CP length G, h, t, andmapping matrix M_(t), a CP extender block may generate {dot over (h)}and {dot over (t)} such that the last T samples (denoted by x₁) andfirst H samples (denoted by x₄) of the vector x shown in the signaldiagram 2830 are approximately equal to T samples until (N−G+1)^(th)sample of x (denoted by x₂) and H samples from (N−G+1)^(th) sample of x(denoted by x₃), respectively, where x₁≅x₃ and x₂≅x₄. The CP may beextended virtually by manipulating the values {dot over (h)} and {dotover (t)}. To achieve this goal, one may partition the waveform matrixA.

FIG. 29 illustrates an example of partitions of the waveform matrix A toderive CP a extender block. FIG. 29 may be read in the context of thevariables as discussed herein, such as with relation to FIGS. 27 and 28.The submatrices may be defined as

A_(H11) = A(1:  H, [1:  M_(d) + M_(t) + M_(h)])A_(H12) = A(1:  H, M_(d) + M_(t) + M_(h) + [1:  M])A_(H21) = A(N − G + [1:  H], [1:  M_(d) + M_(t) + M_(h)])A_(H22) = A(N − G + [1:  H], M_(d) + M_(t) + M_(h) + [1:  M])A_(T11) = A(N − G − T + [1:  T], [1:  M_(d) + M_(t) + M_(h)])A_(T12) = A(N − G − T + [1:  T], M_(d) + M_(t) + M_(h) + [1:  M])A_(T21) = A(N − T + [1:  T], [1:  M_(d) + M_(t) + M_(h)])A_(T22) = A(N − T + [1:  T], M_(d) + M_(t) + M_(h) + [1:  M])

where A(X+[A₁:A₂], Y+[B₁:B₂]) gives the submatrix in A from the rowsfrom X+A₁ to X+A₂ and the columns from Y+B₁ to Y+B₂.

By using the submatrices noted above, vectors x₁, x₂, x₃, and x₄ may beexpressed as

${x_{1} = {{A_{H11}\begin{bmatrix}0 \\t \\h\end{bmatrix}} + {A_{H12}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}}},{x_{2} = {{A_{T11}\begin{bmatrix}0 \\t \\h\end{bmatrix}} + {A_{T12}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}}},{x_{3} = {{A_{H21}\begin{bmatrix}0 \\t \\h\end{bmatrix}} + {A_{H22}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}}},{x_{4} = {{A_{T21}\begin{bmatrix}0 \\t \\h\end{bmatrix}} + {A_{T22}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}}},{\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix} = {\arg\mspace{11mu}{\min\limits_{\lbrack\begin{matrix}\overset{¨}{t} \\\overset{¨}{h}\end{matrix}\rbrack}{{{\begin{bmatrix}{A_{H22} - A_{H12}} \\{A_{T22} - A_{T12}}\end{bmatrix}\begin{bmatrix}\overset{¨}{t} \\\overset{¨}{h}\end{bmatrix}} - {\begin{bmatrix}{A_{H11} - A_{H21}} \\{A_{T11} - A_{T21}}\end{bmatrix}\begin{bmatrix}0 \\t \\h\end{bmatrix}}}}_{2}^{2}}}}$ Subject  to ${\begin{bmatrix}\overset{¨}{t} \\\overset{¨}{h}\end{bmatrix}}_{2}^{2} \leq \alpha$

respectively. Since an objective may be that x₁≅x₃ and x₂≅x₄, byreordering the submatrices, the objective function in the CP extenderblock may be written as

where α is non-negative value that constraints the energy of the CPextending RSs. An equivalent approach for a given α may be obtained inclosed-form in formula (1) below

$\begin{matrix}{\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix} = \underset{\underset{{Operation}\mspace{14mu}{in}\mspace{14mu}{the}\mspace{14mu}{CP}\mspace{14mu}{extender}\mspace{14mu}{block}}{︸}}{\left( {{X^{H}X} + {\lambda I_{R_{t} + R_{h}}}} \right)^{- 1}{{X^{H}\begin{bmatrix}{A_{H11} - A_{H21}} \\{A_{T11} - A_{T21}}\end{bmatrix}}\begin{bmatrix}0 \\t \\h\end{bmatrix}}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

where λ is an non-negative internal parameter of the CP extender block.

FIG. 30 illustrates an example transmission (TX) block diagram withhypothetical values for the purposes of further explaining the CPextender block related concepts. FIG. 30 may be read in the context ofthe variables and processes discussed herein, such as with relation toFIGS. 27, 28, and 29.

FIG. 31 illustrates an example signal that would result from thehypothetical values of the transmission block illustrated in FIG. 30.FIG. 31 may be read in the context of the variables and processesdiscussed herein, such as with relation to FIGS. 27, 28, 29, and 30.

Referring to FIG. 30, let M=96 (i.e., 6 RBs since there may be 96subcarriers in NR), N=512, G=36, and the CP size extended asG_(e)=G+18=54, e.g., H=18 and T=0, samples to increase the robustness ofthe DFT-s-OFDM symbol against multipath channel interference. For thisexample, it may be assumed that the independent RS lengths are given byM_(h)=1 and M_(t)=1 and their values are set to 1 (M_(h) should belarger than M_(h)≥G/N×M to avoid the leakage from data symbols). For themapping, it may be assumed that M_(d1)=86 and M_(d2)=1. The size of thedepended RS may be set as R_(h)=3 and R_(t)=2. Internal λ may be set to0.0001. Given these parameters, referring to FIG. 31, a resulting signalin time domain may be shown where amplitude is shown on the verticalaxis 3102 and the Samples are shown on the horizontal axis 3101. Withthese settings, the CP extender block generates the following CPextending RSs:

$\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix} = \begin{bmatrix}{1.1741 - {0.9584i}} \\{0.5476 - {0.4950i}} \\{0.2776 - {0.2631i}} \\{{- 0.4799} + {0.4480i}} \\{{- 1.4476} + 0.6442}\end{bmatrix}$

As may be seen from the time domain signal, extended CP portions 3114may be approximately the same looking at 3110 a and 3110 b. Hence, thisexample shows that the robustness of DFT-s-OFDM against multipathchannel may be improved with the approaches disclosed herein.

FIG. 32 illustrates an example of doubling CP extensions withCP-extending RSs. For this example, H+T may be equal to G. In order todecrease the error in equation (1), the symbol mapping matrix M_(t) maybe optimized. For example, the mapping matrix M_(t) may interface CPextending RSs and pre-determined RSs.

FIG. 33 illustrates an example of CP extending PT-RS design. In anembodiment, all RS or PT-RSs with an energy constraint may be calculatedby using a CP extender block 3308 and mapped to the input of DFT-s-OFDM.As shown, there may be a detailed transmitter block diagram 3301 and acorresponding time domain symbols 3330 (i.e., three DFT-s-OFDM symbolsback-to-back 3331 _(i−1), 3331 _(i), and 3331 _(i+1)). The CP extenderblock 3308 may generate the vector {dot over (h)} and {dot over (t)}based on a minimization criterion to achieve virtual CP. The output ofthe CP extender block may be calculated offline and may be stored in amemory in the transmitter. After {dot over (h)} and {dot over (t)} aregenerated, d, {dot over (h)}, and {dot over (t)} may be mapped to theinput of M-DFT via symbol mapping matrix M_(t). The overall operationthat generates the vector x may be expressed as

$x = {{F_{N}^{H}M_{f}D_{M}{M_{t}\begin{bmatrix}d \\\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}} = {A\begin{bmatrix}d \\\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}}$

where A=F_(N) ^(H)M_(f)D_(M)M_(t) ∈

^(N×M) is the waveform matrix that generates the vector x from thevector d, h, t, {dot over (h)}, and {dot over (t)}.

FIG. 34 illustrates an example of a signal structure to achieve virtualCP with the CP extender block. The signal structure 3430 with the CPextension portion for achieving virtual CP may be shown when the datavector M_(d) is set to a zero vector. For a given CP length G, andmapping matrix M_(t), the CP extender block may generate {dot over (h)}and {dot over (t)} such that the last T samples (denoted by x₄) andfirst H samples (denoted by x₁) of the vector x are approximately equalto T samples till (N+G+1)^(th) sample of x (denoted by x₂) and H samplesfrom (N−G+1)^(th) sample of x (denoted by x₃), respectively, i.e., x₁≅x₃and x₂≅x₄. The CP may be extended virtually by manipulating the values{dot over (h)} and {dot over (t)}. To achieve this goal, one maypartition the waveform matrix A.

FIG. 35 illustrates waveform matrix A to derive CP extender block forcomplete PT-RS. The submatrices may be defined as

A_(H11) = A(1:H, [1:M_(d)]) A_(H12) = A(1:H, M_(d) + [1:M])A_(H21) = A(N − G + [1:H], [1: M_(d)])A_(H22) = A(N − G + [1:H], M_(d) + [1:M])A_(T11) = A(N − G − T + [1:T], [1: M_(d)])A_(T12) = A(N − G − T + [1:T], M_(d) + [1:M])A_(T21) = A(N − T + [1:T], [1: M_(d)])A_(T22) = A(N − T + [1:T], M_(d) + [1:M])

where A(X+[A₁:A₂], Y+[B₁:B₂]) gives the submatrix in A from the rowsfrom X+A₁ to X+A₂ and the columns from Y+B₁ to Y+B₂.

By using the submatrices noted above, vectors x₁, x₂, x₃, and x₄ may beexpressed as

${x_{1} = {A_{H\; 12}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}},{x_{2} = {A_{T\; 12}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}},{x_{3} = {A_{H\; 22}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}},{and}$ ${x_{4} = {A_{T\; 22}\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix}}},$

respectively. Since one objective may be that x₁≅x₃ and x₂≅x₄, byreordering the submatrices, the operation in CP extender block may bewritten as

$\begin{bmatrix}\overset{.}{t} \\\overset{.}{h}\end{bmatrix} = {\arg\mspace{11mu}{\min\limits_{\lbrack\begin{matrix}\overset{¨}{t} \\\overset{¨}{h}\end{matrix}\rbrack}{{\begin{bmatrix}{A_{H\; 22} - A_{H\; 12}} \\{A_{T\; 22} - A_{T\; 12}}\end{bmatrix}\begin{bmatrix}\overset{¨}{t} \\\overset{¨}{h}\end{bmatrix}}}_{2}^{2}}}$ ${s.t.{\begin{bmatrix}\overset{¨}{t} \\\overset{¨}{h}\end{bmatrix}}_{2}^{2}} \geq \alpha$

where α is non-negative value that avoids of a trivial solution. Thismay be addressed by using any convex optimization toolbox since theproblem is convex.

In another approach, another constraint may be introduced to quantizethe values for the elements {dot over (t)} and {dot over (h)}.

In an embodiment, a PT-RS may be used for or with a sidelinktransmission or sidelink channel. A sidelink channel may be a channelused between WTRUs.

PT-RS is a non-limiting example of an RS that may be used. In theembodiments and examples described herein, another RS such as a DM-RSmay be substituted for PT-RS and still be consistent with thisdisclosure. For example, the solutions used to determine presence,density, and/or location of PT-RS may be applicable to determine thoseof another RS such as DM-RS for a channel such as a sidelink channel.

A sidelink channel or transmission is a non-limiting example of achannel or transmission that may be used for communication between WTRUsthat may be of the same or different type. For example, a backhaulchannel or transmission may be substituted for a sidelink channel ortransmission in the examples and embodiments described herein and stillbe consistent with this disclosure. A backhaul channel or transmissionmay be between gNBs, a relay and a gNB (e.g., a donor gNB), anintegrated access-backhaul (IAB) node, a gNB, IAB nodes, and/or thelike.

In one approach, a PSCCH and a PSSCH may use a same structure (e.g.,DM-RS RE locations and data RE locations within a RB or scheduled RBs).A sidelink transmission may include a PSCCH and its associated PSSCH,where the PSCCH may provide scheduling information for the PSSCH.

The presence (e.g., transmission) of PT-RS in a PSCCH may be determinedbased on the presence of PT-RS in a PSSCH. For example, PT-RS may bepresent (e.g., transmitted) in a PSCCH when PT-RS is present in theassociated PSSCH (e.g., the PSSCH scheduled by the PSCCH).

The presence of PT-RS in a PSCCH may be determined based on the presenceof PT-RS in the associated PSSCH and the time location of the associatedPSCCH. For example, if a PSCCH and its associated PSSCH (e.g., scheduledPSSCH by the PSCCH) are located in the same slot, or a same timelocation, and the associated PSSCH include a PT-RS, the PSSCH mayinclude the PT-RS. If a PSCCH and its associated PSSCH are located in adifferent slot, or a different time location, the PSCCH may not includea PT-RS.

The presence of PT-RS in a PSSCH may be determined based on at least oneof the following: a frequency range (e.g., FR1, FR2) of a carrier orbandwidth part for a sidelink transmission (e.g., for the PSSCH); asubcarrier spacing of the carrier or BWP for the PSSCH transmission or asubcarrier spacing that may be used for the PSSCH transmission; an MCSlevel and/or scheduling bandwidth indicated or used for the PSSCH;Doppler frequency (or relative speed between two WTRUs); and/or a higherlayer configuration.

The density of PT-RS (e.g., time and/or frequency density) for a PSCCHmay be determined based on the density of PT-RS for the associatedPSSCH. Additionally/alternatively, the density of PT-RS for the PSCCHmay be the same as the density of the PT-RS for the associated PSSCH.Additionally/alternatively, the density of PT-RS for the associatedPSSCH may be determined based on a higher layer configuration.Additionally/alternatively, the density of PT-RS for the associatedPSSCH may be determined based on the distance, or proximity, between twoWTRUs, wherein the WTRUs may be informed about the distance information,or proximity information, from the gNB which may grant the sidelinkresource. Additionally/alternatively, the density of PT-RS for theassociated PSSCH may be determined based on one or more schedulingparameters (e.g., MCS level, scheduling bandwidth).

The one or more scheduling parameters for a PSSCH which may determinePT-RS density of PSSCH and/or PSCCH may be configured (e.g.,preconfigured) or indicated before a WTRU sends a PSCCH. For example, aPDCCH (e.g., a PDCCH that grants one or more sidelink resources) mayprovide or indicate one or more pieces of scheduling information for aPSSCH that may determine or may be used to determine PT-RS density forPSCCH and/or PSSCH.

One or more PSCCHs may be associated with a PSSCH, wherein a sidelinkcontrol information (SCI) that schedules a PSSCH may be split into oneor more PSCCH. For example, a first subset of SCI may be transmitted ina first PSCCH and a second subset of SCI may be transmitted in a secondPSCCH, and so on. The first PSCCH may include PT-RS. The density and/orlocation of the PT-RS of the first PSCCH may be configured orpredetermined. Alternatively, the first PSCCH may not include PT-RS.Additionally/alternatively the first PSCCH may include one or morepieces of scheduling information for a PSSCH that may determine or maybe used to determine PT-RS density and/or PT-RS location of the PSSCH.One or more pieces of scheduling information included in a PSCCH (e.g.,the first PSCCH) may determine or be used to determine the PT-RS densityand/or PT-RS location of another PSCCH, such as one or more (e.g., all)of the rest of the PSCCH(s).

The presence and/or density of PT-RS for a PSCCH may be determined orpredetermined based on the PSCCH configuration. The presence and/ordensity of PT-RS for a PSSCH may be determined based on a schedulingparameter provided by the associated PSCCH.

In one scenario, when a PSCCH is used to schedule a PSSCH, a schedulingparameter (e.g., MCS or scheduling bandwidth) of the PSSCH may not beknown, for example until after the PSCCH is received. A maximum orminimum value for a scheduling parameter (e.g., for a PSSCH) may beconfigured and/or used to determine the presence and/or density of thePT-RS for the PSCCH.

In an approach, a PSCCH and/or a PSSCH resource may be determined,indicated, and/or granted by a PDCCH. The presence and/or density ofPT-RS for a PSCCH may be determined based on information provided by theassociated PDCCH. The presence and/or density of PT-RS for a PSSCH maybe determined based on the information provided by the associated PSCCH.

A PDCCH (e.g., a DCI) for a PSCCH resource allocation or grant mayinclude one or more of the following: time/frequency location of one ormore PSCCH; a number of RBs used for a PSCCH transmission; DM-RSconfiguration information (e.g., a DM-RS density of a PSCCH, DM-RSlocations within a PSCCH, etc.); and/or, PT-RS configuration information(e.g., presence of a PT-RS, PT-RS density, PT-RS locations including RBoffset and subcarrier location).

A PSCCH for a PSSCH scheduling may include one or more of following:time/frequency location of the scheduled PSSCH; a number of RBs used forthe scheduled PSSCH; DM-RS configuration information (e.g., a DM-RSdensity of a PSSCH, DM-RS locations within a PSSCH, etc.); PT-RSconfiguration information (e.g., presence of a PT-RS, PT-RS density,PT-RS locations including RB offset and subcarrier location); and/or, ifthe PT-RS configuration information is not provided by the associatedPSCCH, the PT-RS configuration may be the same as that for PSCCH.

One or more modes of operation may be used for a sidelink. In a firstsidelink mode (e.g., SL-Mode-1), the resources for PSCCH and/or PSSCHmay be dynamically granted by a gNB (e.g., using a PDCCH). In a secondsidelink mode (e.g., SL-Mode-2), one or more resources for PSCCH and/orPSCCH may be configured (e.g., preconfigured) and a WTRU may determineand/or use one of the configured resources.

In the examples and embodiments described herein a first mode may be amode with dynamically granted resources (e.g., SL-Mode-1) and a secondmode may be a mode with WTRU selected resources from a configured poolor set (e.g., SL-Mode-2) or vice versa.

In a solution, the presence, density, and/or location of PT-RS for asidelink channel (e.g., PSCCH and/or PSSCH) may be determined based onthe sidelink mode of operation. For example, the presence of a PT-RS ina sidelink channel may be determined based on the sidelink mode ofoperation. PT-RS may be present in a sidelink channel in a firstsidelink mode and may not be present in the sidelink channel in a secondsidelink mode

A density and/or location of the PT-RS for the sidelink channel may beconfigured (e.g., via higher layer signaling) or may be determined asdescribed in examples herein (e.g., based on one or more transmissionparameters such as a frequency range, subcarrier spacing, MCS level,scheduling bandwidth, or the like).

The means for determining (e.g., which means to use for determining) thedensity and/or location of the PT-RS of a sidelink channel may bedetermined based on a sidelink mode. A means may be an explicit meanssuch as configuration or signaling (e.g., of the density and/orlocation). A means may be an implicit means such as determination basedon one or more parameters (e.g., that are not explicitly the densityand/or location). For example the density and/or location of the PT-RSof a sidelink channel may be configured (e.g., by higher layersignaling) for a first sidelink mode. For a second sidelink mode, thedensity and/or location of the PT-RS of a sidelink channel may bedetermined based on one or more transmission parameters such as afrequency range, subcarrier spacing, MCS level, scheduling bandwidth,and the like.

In a solution, the presence, density, and/or location of PT-RS for asidelink channel (e.g., PSCCH and/or PSSCH) may be determined based onone or more of the following transmission parameters: a relative speedbetween WTRUs; a coverage level (e.g., proximity level) between WTRUs; ageographical location of a WTRU (e.g., Tx WTRU) in a cell; a number ofsymbols used for a sidelink channel; a frequency range; a time/frequencylocation or sidelink resource index or identity of a determined sidelinkresource where the sidelink resource may be determined based onscheduling, configuration, and/or selection; a DM-RS density (e.g.,number of symbols used for a DM-RS); and/or a search space used for thechannel or an associated channel (e.g., a search space of an associatedPSCCH channel when transmitting the PT-RS in or with the PSSCH).

In an example, one or more sidelink resources may be configured (e.g.,preconfigured) and a (e.g., each) sidelink resource may be associatedwith a sidelink resource identity (e.g., SL-id). A WTRU may determine asidelink resource for transmission or reception. A presence, density,and/or location of PT-RS for a sidelink channel (e.g., PSCCH, PSSCH) maybe determined based on the determined sidelink resource identity.

The location of PT-RS may include one or more RB locations and/or one ormore subcarrier locations.

In a solution, the presence, density, and/or location of PT-RS for asidelink channel (e.g., PSCCH and/or PSSCH) may be determined based on aDM-RS density (e.g., a number of symbols used for a DM-RS). In anexample, if a DM-RS density of a sidelink channel is below a threshold,a PT-RS may not present in the sidelink channel; otherwise a PT-RS maypresent in the sidelink channel. In another example, if a DM-RS densityof a sidelink channel is below a threshold, a first PT-RS density may beused for the sidelink channel; otherwise, a second PT-RS density may beused for the sidelink channel. A DM-RS density of a sidelink channel maybe indicated in the associated PDCCH for the sidelink channel resourceallocation (e.g., SL-Mode-1).

In a solution, an RB offset of a PT-RS for a sidelink channel may bedetermined based on a WTRU identity (WTRU-id) of a transmitter WTRU or areceiver WTRU. Alternatively, an RB offset of PT-RS for a sidelinkchannel may be determined based on a destination identity, wherein thedestination identity may be a group ID (e.g., ProSe group ID) for whichthe sidelink channel may be transmitted. A WTRU-id may be a RNTI (e.g.,C-RNTI, SL-RNTI) assigned for a WTRU (i.e., transmitter WTRU or receiverWTRU). A WTRU-id and/or a group ID may be provided in a resource grant(e.g., from PDCCH) for a sidelink transmission.

In another solution, an RB offset of a PT-RS for a channel (e.g., asidelink channel) may be determined based on at least one of: ascrambling code or sequence (e.g., an index or identity of thescrambling code or sequence) that may be used for transmission of thechannel; a DM-RS (e.g., an index or identity of the DM-RS such as theindex or identity of the DM-RS sequence) that may be transmitted withthe channel; and/or a search space used for the channel or an associatedchannel (e.g., a search space of associated PSCCH channel whentransmitting the PT-RS in or with a PSSCH).

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

1. A method implemented by a wireless transmit/receive unit (WTRU), themethod comprising: receiving control information indicating that one ormore phase tracking reference signals (PT-RSs) are to be comprised in aphysical uplink shared channel (PUSCH) transmission; generating a PT-RSsequence for the one or more PT-RSs, wherein phase shifts applied toPT-RS bits of the PT-RS sequence are based on one or more indicesassociated with one or more inputs to a discrete Fourier transform (DFT)used to process the one or more PT-RSs; and transmitting the PUSCHtransmission comprising the one or more PT-RSs.
 2. The method of claim1, wherein the PUSCH transmission is transmitted as a DFT spreadorthogonal frequency division multiplexing (DFT-s-OFDM) waveform.
 3. Themethod of claim 1, wherein the PT-RS bits are modulated using binaryphase shift keying (BPSK) modulation.
 4. The method of claim 3, whereinthe PT-RS bits are modulated using BPSK modulation prior to applying anorthogonal cover code (OCC) to the BPSK-modulated PT-RS bits, andwherein a pi/2 modulation is applied to the BPSK-modulated PT-RS bitsafter the OCC is applied to the BPSK-modulated PT-RS bits.
 5. The methodof claim 4, wherein the OCC to apply to the BPSK-modulated PT-RS bits isdetermined based on a WTRU ID of the WTRU.
 6. The method of claim 1,wherein the PT-RS bits are modulated using pi/2 binary phase shiftkeying (BPSK) modulation and data comprised in the PUSCH transmission ismodulated using quadrature phase shift keying (QPSK) modulation.
 7. Themethod of claim 1, wherein a PT-RS density in the frequency domain ofthe one or more PT-RSs is dependent on a number of schedule resourceblocks (RBs) for the PUSCH transmission.
 8. The method of claim 1,wherein the phase shifts applied to the PT-RS bits correspond toconstellations of a pi/2 modulation scheme.
 9. The method of claim 1,the control information indicating that the one or more PT-RSs are to becomprised in the PUSCH transmission is received in a radio resourcecontrol (RRC) message.
 10. The method of claim 1, further comprisingreceiving downlink control information (DCI), the DCI comprisingscheduling information for the PUSCH transmission.
 11. The method ofclaim 1, wherein the phase shifts applied to the PT-RS bits arerepresented by ${e^{\frac{jn\pi}{2}}\frac{1}{\sqrt{2}}},$ where nrepresents the one or more indices associated with the one or moreinputs to the DFT used to process the PT-RSs bits.
 12. The method ofclaim 1, wherein the PT-RS sequence is generated based on a pseudorandomsequence generator.
 13. A wireless transmit/receive unit (WTRU), theWTRU comprising: a processor configured to: receive control informationindicating that one or more phase tracking reference signals (PT-RSs)are to be comprised in a physical uplink shared channel (PUSCH)transmission; generate a PT-RS sequence for the one or more PT-RSs,wherein phase shifts applied to PT-RS bits of the PT-RS sequence arebased on one or more indices associated with one or more inputs to adiscrete Fourier transform (DFT) used to process the one or more PT-RSs;and transmit the PUSCH transmission comprising the one or more PT-RSs.14. The WTRU of claim 13, wherein the PUSCH transmission is transmittedas a DFT spread orthogonal frequency division multiplexing (DFT-s-OFDM)waveform.
 15. The WTRU of claim 13, wherein the PT-RS bits are modulatedusing binary phase shift keying (BPSK) modulation.
 16. The WTRU of claim15, wherein the PT-RS bits are modulated using BPSK modulation prior toapplying an orthogonal cover code (OCC) to the BPSK-modulated PT-RSbits, and wherein a pi/2 modulation is applied to the BPSK-modulatedPT-RS bits after the OCC is applied to the BPSK-modulated PT-RS bits.17. The WTRU of claim 16, wherein the OCC to apply to the BPSK-modulatedPT-RS bits is determined based on a WTRU ID of the WTRU.
 18. The WTRU ofclaim 13, wherein the control information indicates that the one or morePT-RSs are to be comprised in the PUSCH transmission is received in aradio resource control (RRC) message.
 19. The WTRU of claim 13, whereinthe phase shifts applied to the PT-RS bits are represented by${e^{\frac{jn\pi}{2}}\frac{1}{\sqrt{2}}},$ where n represents the one ormore indices associated with the one or more inputs to the DFT used toprocess the PT-RSs bits.
 20. The WTRU of claim 13, wherein the PT-RSsequence is generated based on a pseudorandom sequence generator.